<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019ef506-4300-7c47-9111-cf33c1ec03fd,g:c865e5fb-33b8-40f0-80a4-96d73afb2011-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.busey.com/role/Cover" xlink:type="simple" xlink:href="buse-20260629.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_019ef506-4300-7cc2-b1f7-85a48d1cd4a8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019ef506-4300-7b6e-b972-5876cdae80e8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_019ef506-4300-7cc2-b1f7-85a48d1cd4a8" xlink:to="loc_dei_DocumentInformationTable_019ef506-4300-7b6e-b972-5876cdae80e8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-4300-7b28-86d4-40b4209a1ca6" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_019ef506-4300-7b6e-b972-5876cdae80e8" xlink:to="loc_dei_LegalEntityAxis_019ef506-4300-7b28-86d4-40b4209a1ca6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-4300-7b28-86d4-40b4209a1ca6_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-4300-7b28-86d4-40b4209a1ca6" xlink:to="loc_dei_EntityDomain_019ef506-4300-7b28-86d4-40b4209a1ca6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-4300-7ec7-9943-d1ddd271b1a0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-4300-7b28-86d4-40b4209a1ca6" xlink:to="loc_dei_EntityDomain_019ef506-4300-7ec7-9943-d1ddd271b1a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-4300-7b33-b325-a9e240fafa23" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-4300-7ec7-9943-d1ddd271b1a0" xlink:to="loc_buse_EBP002Member_019ef506-4300-7b33-b325-a9e240fafa23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019ef506-4300-758e-aad2-ed087e0bb996" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ef506-4300-7cc2-b1f7-85a48d1cd4a8" xlink:to="loc_dei_DocumentType_019ef506-4300-758e-aad2-ed087e0bb996" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019ef506-4300-779e-9ef3-49b7d1d47ecf" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ef506-4300-7cc2-b1f7-85a48d1cd4a8" xlink:to="loc_dei_EntityRegistrantName_019ef506-4300-779e-9ef3-49b7d1d47ecf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019ef506-4300-7dae-8f12-725cbdc3d916" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ef506-4300-7cc2-b1f7-85a48d1cd4a8" xlink:to="loc_dei_EntityCentralIndexKey_019ef506-4300-7dae-8f12-725cbdc3d916" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019ef506-4300-7ccc-87f8-cd60ffdd7ab1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019ef506-4300-7cc2-b1f7-85a48d1cd4a8" xlink:to="loc_dei_AmendmentFlag_019ef506-4300-7ccc-87f8-cd60ffdd7ab1" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/StatementsofNetAssetsAvailableforBenefits" xlink:type="simple" xlink:href="buse-20260629.xsd#StatementsofNetAssetsAvailableforBenefits"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/StatementsofNetAssetsAvailableforBenefits" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfNetAssetAvailableForBenefitLineItems_019ef506-4300-745d-a5b7-6465574fac80" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanStatementOfNetAssetAvailableForBenefitLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfNetAssetAvailableForBenefitTable_019ef506-4300-73bf-80c3-01b7016da817" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanStatementOfNetAssetAvailableForBenefitTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfNetAssetAvailableForBenefitLineItems_019ef506-4300-745d-a5b7-6465574fac80" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfNetAssetAvailableForBenefitTable_019ef506-4300-73bf-80c3-01b7016da817" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-4300-7915-a3f4-91fae06ec4f4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfNetAssetAvailableForBenefitTable_019ef506-4300-73bf-80c3-01b7016da817" xlink:to="loc_dei_LegalEntityAxis_019ef506-4300-7915-a3f4-91fae06ec4f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-4300-7915-a3f4-91fae06ec4f4_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-4300-7915-a3f4-91fae06ec4f4" xlink:to="loc_dei_EntityDomain_019ef506-4300-7915-a3f4-91fae06ec4f4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-4300-7a91-acb8-b954ac7d9c63" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-4300-7915-a3f4-91fae06ec4f4" xlink:to="loc_dei_EntityDomain_019ef506-4300-7a91-acb8-b954ac7d9c63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-4300-7578-915b-a4a5973bb81a" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-4300-7a91-acb8-b954ac7d9c63" xlink:to="loc_buse_EBP002Member_019ef506-4300-7578-915b-a4a5973bb81a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAssetAbstract_019ef506-4300-795b-b73b-1cde2a91576d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAssetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfNetAssetAvailableForBenefitLineItems_019ef506-4300-745d-a5b7-6465574fac80" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanAssetAbstract_019ef506-4300-795b-b73b-1cde2a91576d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentExcludingPlanInterestInMasterTrustFairValue_019ef506-4300-7d5f-986e-6b3008edfbd2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentExcludingPlanInterestInMasterTrustFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAssetAbstract_019ef506-4300-795b-b73b-1cde2a91576d" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentExcludingPlanInterestInMasterTrustFairValue_019ef506-4300-7d5f-986e-6b3008edfbd2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanCash_019ef506-4300-7224-bfc3-ab5f45d9ecc0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAssetAbstract_019ef506-4300-795b-b73b-1cde2a91576d" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanCash_019ef506-4300-7224-bfc3-ab5f45d9ecc0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanReceivableAbstract_019ef506-4300-7ee5-a6c7-f24c8d851022" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanReceivableAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAssetAbstract_019ef506-4300-795b-b73b-1cde2a91576d" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanReceivableAbstract_019ef506-4300-7ee5-a6c7-f24c8d851022" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerContributionReceivable_019ef506-4300-7f21-b8bc-00ca9f05315c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanEmployerContributionReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanReceivableAbstract_019ef506-4300-7ee5-a6c7-f24c8d851022" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerContributionReceivable_019ef506-4300-7f21-b8bc-00ca9f05315c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanParticipantContributionReceivable_019ef506-4300-7050-a1cb-75cb5ba4bc28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanParticipantContributionReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanReceivableAbstract_019ef506-4300-7ee5-a6c7-f24c8d851022" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanParticipantContributionReceivable_019ef506-4300-7050-a1cb-75cb5ba4bc28" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipant_019ef506-4300-73b1-9d12-7a921e223b5a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanReceivableAbstract_019ef506-4300-7ee5-a6c7-f24c8d851022" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipant_019ef506-4300-73b1-9d12-7a921e223b5a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanReceivable_019ef506-4300-7bfe-bd34-1cb50acc1c50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanReceivableAbstract_019ef506-4300-7ee5-a6c7-f24c8d851022" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanReceivable_019ef506-4300-7bfe-bd34-1cb50acc1c50" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanNetAssetAvailableForBenefit_019ef506-4300-72bb-aae9-cc6031295d7a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanNetAssetAvailableForBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfNetAssetAvailableForBenefitLineItems_019ef506-4300-745d-a5b7-6465574fac80" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanNetAssetAvailableForBenefit_019ef506-4300-72bb-aae9-cc6031295d7a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/StatementofChangesinNetAssetsAvailableforBenefits" xlink:type="simple" xlink:href="buse-20260629.xsd#StatementofChangesinNetAssetsAvailableforBenefits"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/StatementofChangesinNetAssetsAvailableforBenefits" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitLineItems_019ef506-4300-7968-b89b-705ebd1558f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitTable_019ef506-4300-7657-aa94-ccc138e19f21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitLineItems_019ef506-4300-7968-b89b-705ebd1558f7" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitTable_019ef506-4300-7657-aa94-ccc138e19f21" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-4300-7cfc-91d8-223d7c3a875b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitTable_019ef506-4300-7657-aa94-ccc138e19f21" xlink:to="loc_dei_LegalEntityAxis_019ef506-4300-7cfc-91d8-223d7c3a875b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-4300-7cfc-91d8-223d7c3a875b_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-4300-7cfc-91d8-223d7c3a875b" xlink:to="loc_dei_EntityDomain_019ef506-4300-7cfc-91d8-223d7c3a875b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-4300-7445-9f89-6aab847cd122" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-4300-7cfc-91d8-223d7c3a875b" xlink:to="loc_dei_EntityDomain_019ef506-4300-7445-9f89-6aab847cd122" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-4300-73fb-b565-52fb7a168f7d" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-4300-7445-9f89-6aab847cd122" xlink:to="loc_buse_EBP002Member_019ef506-4300-73fb-b565-52fb7a168f7d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseAbstract_019ef506-4300-711d-b82d-c162f2c89700" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitLineItems_019ef506-4300-7968-b89b-705ebd1558f7" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseAbstract_019ef506-4300-711d-b82d-c162f2c89700" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForIncomeLossOnInvestmentAbstract_019ef506-4300-7b1d-ba07-f1a70348da9b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForIncomeLossOnInvestmentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseAbstract_019ef506-4300-711d-b82d-c162f2c89700" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForIncomeLossOnInvestmentAbstract_019ef506-4300-7b1d-ba07-f1a70348da9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForGainLossOnInvestment_019ef506-4300-79c5-a7b0-9747112a07bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForGainLossOnInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForIncomeLossOnInvestmentAbstract_019ef506-4300-7b1d-ba07-f1a70348da9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForGainLossOnInvestment_019ef506-4300-79c5-a7b0-9747112a07bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForInterestAndDividendIncomeOnInvestment_019ef506-4300-76b4-8a46-8103055fc1c7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForInterestAndDividendIncomeOnInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForIncomeLossOnInvestmentAbstract_019ef506-4300-7b1d-ba07-f1a70348da9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForInterestAndDividendIncomeOnInvestment_019ef506-4300-76b4-8a46-8103055fc1c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForIncomeLossOnInvestment_019ef506-4300-7427-b386-41732f7e9b16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForIncomeLossOnInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForIncomeLossOnInvestmentAbstract_019ef506-4300-7b1d-ba07-f1a70348da9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForIncomeLossOnInvestment_019ef506-4300-7427-b386-41732f7e9b16" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForInterestIncomeOnNoteReceivableFromParticipant_019ef506-4300-7e18-9988-a73c4e57f311" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForInterestIncomeOnNoteReceivableFromParticipant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseAbstract_019ef506-4300-711d-b82d-c162f2c89700" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForInterestIncomeOnNoteReceivableFromParticipant_019ef506-4300-7e18-9988-a73c4e57f311" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForContributionAbstract_019ef506-4300-74de-ad8d-95c1a6e4c4de" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForContributionAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseAbstract_019ef506-4300-711d-b82d-c162f2c89700" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForContributionAbstract_019ef506-4300-74de-ad8d-95c1a6e4c4de" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForEmployerContributionCash_019ef506-4300-7926-89d8-ed5b774dbea0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForEmployerContributionCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForContributionAbstract_019ef506-4300-74de-ad8d-95c1a6e4c4de" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForEmployerContributionCash_019ef506-4300-7926-89d8-ed5b774dbea0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForParticipantContributionExcludingRollover_019ef506-4300-74e4-9b5c-8b7e1d3b2717" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForParticipantContributionExcludingRollover"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForContributionAbstract_019ef506-4300-74de-ad8d-95c1a6e4c4de" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForParticipantContributionExcludingRollover_019ef506-4300-74e4-9b5c-8b7e1d3b2717" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForParticipantContributionRollover_019ef506-4300-7686-a7a4-41f421f113b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForParticipantContributionRollover"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForContributionAbstract_019ef506-4300-74de-ad8d-95c1a6e4c4de" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForParticipantContributionRollover_019ef506-4300-7686-a7a4-41f421f113b1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForContribution_019ef506-4300-76de-91d5-5f19172c734a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForContribution"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForContributionAbstract_019ef506-4300-74de-ad8d-95c1a6e4c4de" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForContribution_019ef506-4300-76de-91d5-5f19172c734a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncrease_019ef506-4300-7566-86d5-a601e6f164be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseAbstract_019ef506-4300-711d-b82d-c162f2c89700" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncrease_019ef506-4300-7566-86d5-a601e6f164be" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseAbstract_019ef506-4300-76ed-9a09-b1f0f7a3f733" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitLineItems_019ef506-4300-7968-b89b-705ebd1558f7" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseAbstract_019ef506-4300-76ed-9a09-b1f0f7a3f733" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseForPaymentToParticipant_019ef506-4300-7d65-85af-c7cdd5a3c262" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseForPaymentToParticipant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseAbstract_019ef506-4300-76ed-9a09-b1f0f7a3f733" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseForPaymentToParticipant_019ef506-4300-7d65-85af-c7cdd5a3c262" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseForAdministrativeExpense_019ef506-4300-7bf8-8a2d-ecf01e55ccd0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseForAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseAbstract_019ef506-4300-76ed-9a09-b1f0f7a3f733" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseForAdministrativeExpense_019ef506-4300-7bf8-8a2d-ecf01e55ccd0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecrease_019ef506-4300-7893-bf77-0bf40d488be9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecreaseAbstract_019ef506-4300-76ed-9a09-b1f0f7a3f733" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecrease_019ef506-4300-7893-bf77-0bf40d488be9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecrease_019ef506-4300-7736-9b9e-2f4deb171101" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitLineItems_019ef506-4300-7968-b89b-705ebd1558f7" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecrease_019ef506-4300-7736-9b9e-2f4deb171101" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPNetAssetAvailableForBenefitAbstract_019ef506-4300-77ec-81f6-12a043c0d0c4" xlink:href="buse-20260629.xsd#buse_EBPNetAssetAvailableForBenefitAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanStatementOfChangeInNetAssetAvailableForBenefitLineItems_019ef506-4300-7968-b89b-705ebd1558f7" xlink:to="loc_buse_EBPNetAssetAvailableForBenefitAbstract_019ef506-4300-77ec-81f6-12a043c0d0c4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanNetAssetAvailableForBenefit_019ef506-4300-78a4-90a0-c056d6f8667f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanNetAssetAvailableForBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_buse_EBPNetAssetAvailableForBenefitAbstract_019ef506-4300-77ec-81f6-12a043c0d0c4" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanNetAssetAvailableForBenefit_019ef506-4300-78a4-90a0-c056d6f8667f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanNetAssetAvailableForBenefit_019ef506-4300-72ed-b891-3d3745086907" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanNetAssetAvailableForBenefit"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/PLANDESCRIPTION" xlink:type="simple" xlink:href="buse-20260629.xsd#PLANDESCRIPTION"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/PLANDESCRIPTION" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-751e-bfec-68a0f2989814" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTable_019ef506-4300-7aa7-a34c-5dd176d4cf2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-751e-bfec-68a0f2989814" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTable_019ef506-4300-7aa7-a34c-5dd176d4cf2d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-4300-7235-9ff2-a5ccdf70ecda" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTable_019ef506-4300-7aa7-a34c-5dd176d4cf2d" xlink:to="loc_dei_LegalEntityAxis_019ef506-4300-7235-9ff2-a5ccdf70ecda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-4300-7235-9ff2-a5ccdf70ecda_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-4300-7235-9ff2-a5ccdf70ecda" xlink:to="loc_dei_EntityDomain_019ef506-4300-7235-9ff2-a5ccdf70ecda_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-4300-7f5d-b7ff-cc3e17242933" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-4300-7235-9ff2-a5ccdf70ecda" xlink:to="loc_dei_EntityDomain_019ef506-4300-7f5d-b7ff-cc3e17242933" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-4300-74c0-84be-919d1fb95214" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-4300-7f5d-b7ff-cc3e17242933" xlink:to="loc_buse_EBP002Member_019ef506-4300-74c0-84be-919d1fb95214" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTextBlock_019ef506-4300-749a-b60f-e6654dd0b116" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-751e-bfec-68a0f2989814" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTextBlock_019ef506-4300-749a-b60f-e6654dd0b116" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/SIGNIFICANTACCOUNTINGPOLICIES" xlink:type="simple" xlink:href="buse-20260629.xsd#SIGNIFICANTACCOUNTINGPOLICIES"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/SIGNIFICANTACCOUNTINGPOLICIES" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-7ce8-b3e2-78dea021dc2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable_019ef506-43b6-7068-a437-f56f8ce4decd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-7ce8-b3e2-78dea021dc2d" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable_019ef506-43b6-7068-a437-f56f8ce4decd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-7120-8788-39e744dea8f4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable_019ef506-43b6-7068-a437-f56f8ce4decd" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-7120-8788-39e744dea8f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7120-8788-39e744dea8f4_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7120-8788-39e744dea8f4" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7120-8788-39e744dea8f4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-74d6-beb9-bc489c15f93b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7120-8788-39e744dea8f4" xlink:to="loc_dei_EntityDomain_019ef506-43b6-74d6-beb9-bc489c15f93b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-765a-a5fc-4331b1488ba8" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-74d6-beb9-bc489c15f93b" xlink:to="loc_buse_EBP002Member_019ef506-43b6-765a-a5fc-4331b1488ba8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanSummaryOfAccountingPolicyTextBlock_019ef506-43b6-7e74-af62-3a6e5c9cd0b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanSummaryOfAccountingPolicyTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-7ce8-b3e2-78dea021dc2d" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanSummaryOfAccountingPolicyTextBlock_019ef506-43b6-7e74-af62-3a6e5c9cd0b6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/FAIRVALUEMEASUREMENTS" xlink:type="simple" xlink:href="buse-20260629.xsd#FAIRVALUEMEASUREMENTS"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/FAIRVALUEMEASUREMENTS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems_019ef506-43b6-7683-ae2d-779f707b1faa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7bb3-9f6a-5c66e7b7ba4b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems_019ef506-43b6-7683-ae2d-779f707b1faa" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7bb3-9f6a-5c66e7b7ba4b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-7f83-afe2-c090828d5cb5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7bb3-9f6a-5c66e7b7ba4b" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-7f83-afe2-c090828d5cb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7f83-afe2-c090828d5cb5_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7f83-afe2-c090828d5cb5" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7f83-afe2-c090828d5cb5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7dd5-8b60-e9cbb6e66b30" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7f83-afe2-c090828d5cb5" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7dd5-8b60-e9cbb6e66b30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-7a43-82f8-f39ecc07198f" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-7dd5-8b60-e9cbb6e66b30" xlink:to="loc_buse_EBP002Member_019ef506-43b6-7a43-82f8-f39ecc07198f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTextBlock_019ef506-43b6-7390-9d55-5e382cd6ade4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems_019ef506-43b6-7683-ae2d-779f707b1faa" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTextBlock_019ef506-43b6-7390-9d55-5e382cd6ade4" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/PARTYININTERESTTRANSACTIONS" xlink:type="simple" xlink:href="buse-20260629.xsd#PARTYININTERESTTRANSACTIONS"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/PARTYININTERESTTRANSACTIONS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-7b76-a8e8-432923c144f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-7e56-b09a-ac349fe70944" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-7b76-a8e8-432923c144f3" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-7e56-b09a-ac349fe70944" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-77bd-8323-99bfaec8b6bb" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-7e56-b09a-ac349fe70944" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-77bd-8323-99bfaec8b6bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-77bd-8323-99bfaec8b6bb_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-77bd-8323-99bfaec8b6bb" xlink:to="loc_dei_EntityDomain_019ef506-43b6-77bd-8323-99bfaec8b6bb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-79d1-b9bf-429ec1ca5f75" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-77bd-8323-99bfaec8b6bb" xlink:to="loc_dei_EntityDomain_019ef506-43b6-79d1-b9bf-429ec1ca5f75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-7978-9e16-422d42656bfd" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-79d1-b9bf-429ec1ca5f75" xlink:to="loc_buse_EBP002Member_019ef506-43b6-7978-9e16-422d42656bfd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTextBlock_019ef506-43b6-70b6-955f-0e24379663ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-7b76-a8e8-432923c144f3" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTextBlock_019ef506-43b6-70b6-955f-0e24379663ab" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/INCOMETAXSTATUS" xlink:type="simple" xlink:href="buse-20260629.xsd#INCOMETAXSTATUS"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/INCOMETAXSTATUS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanTaxStatusLineItems_019ef506-43b6-7e84-8b16-2d50da32ec10" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanTaxStatusLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanTaxStatusTable_019ef506-43b6-7d40-a150-f2e61ba623b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanTaxStatusTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanTaxStatusLineItems_019ef506-43b6-7e84-8b16-2d50da32ec10" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanTaxStatusTable_019ef506-43b6-7d40-a150-f2e61ba623b2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-71ce-a555-5766cd99be13" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanTaxStatusTable_019ef506-43b6-7d40-a150-f2e61ba623b2" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-71ce-a555-5766cd99be13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-71ce-a555-5766cd99be13_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-71ce-a555-5766cd99be13" xlink:to="loc_dei_EntityDomain_019ef506-43b6-71ce-a555-5766cd99be13_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-75ed-8b7b-c543c5626adf" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-71ce-a555-5766cd99be13" xlink:to="loc_dei_EntityDomain_019ef506-43b6-75ed-8b7b-c543c5626adf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-7a8d-9594-f8c61f89df45" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-75ed-8b7b-c543c5626adf" xlink:to="loc_buse_EBP002Member_019ef506-43b6-7a8d-9594-f8c61f89df45" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanTaxStatusTextBlock_019ef506-43b6-75e9-ae0b-038ff23529c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanTaxStatusTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanTaxStatusLineItems_019ef506-43b6-7e84-8b16-2d50da32ec10" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanTaxStatusTextBlock_019ef506-43b6-75e9-ae0b-038ff23529c9" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/PLANTERMINATION" xlink:type="simple" xlink:href="buse-20260629.xsd#PLANTERMINATION"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/PLANTERMINATION" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanFullyBenefitResponsiveInvestmentContractLineItems_019ef506-43b6-79fa-85f4-0f3826f87048" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanFullyBenefitResponsiveInvestmentContractLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanFullyBenefitResponsiveInvestmentContractTable_019ef506-43b6-7aaa-b2ea-04bd6390cbe3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanFullyBenefitResponsiveInvestmentContractTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanFullyBenefitResponsiveInvestmentContractLineItems_019ef506-43b6-79fa-85f4-0f3826f87048" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanFullyBenefitResponsiveInvestmentContractTable_019ef506-43b6-7aaa-b2ea-04bd6390cbe3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-784c-a389-c2d1cfe90357" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanFullyBenefitResponsiveInvestmentContractTable_019ef506-43b6-7aaa-b2ea-04bd6390cbe3" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-784c-a389-c2d1cfe90357" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-784c-a389-c2d1cfe90357_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-784c-a389-c2d1cfe90357" xlink:to="loc_dei_EntityDomain_019ef506-43b6-784c-a389-c2d1cfe90357_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7dcb-a95c-0ccbd5922ef2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-784c-a389-c2d1cfe90357" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7dcb-a95c-0ccbd5922ef2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-7f69-b66b-0fc64cc8ed19" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-7dcb-a95c-0ccbd5922ef2" xlink:to="loc_buse_EBP002Member_019ef506-43b6-7f69-b66b-0fc64cc8ed19" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanPlanTerminationTextBlock_019ef506-43b6-7054-9fbd-e127ad00108e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanPlanTerminationTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanFullyBenefitResponsiveInvestmentContractLineItems_019ef506-43b6-79fa-85f4-0f3826f87048" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanPlanTerminationTextBlock_019ef506-43b6-7054-9fbd-e127ad00108e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/RECENTLEGISLATION" xlink:type="simple" xlink:href="buse-20260629.xsd#RECENTLEGISLATION"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/RECENTLEGISLATION" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EbpContingencyLineItems_019ef506-43b6-7d03-971e-8ac04bd31187" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EbpContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EbpContingencyTable_019ef506-43b6-71be-b161-838e312ada57" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EbpContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EbpContingencyLineItems_019ef506-43b6-7d03-971e-8ac04bd31187" xlink:to="loc_us-gaap-ebp_EbpContingencyTable_019ef506-43b6-71be-b161-838e312ada57" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-7ff2-996b-e2e767711674" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EbpContingencyTable_019ef506-43b6-71be-b161-838e312ada57" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-7ff2-996b-e2e767711674" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7ff2-996b-e2e767711674_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7ff2-996b-e2e767711674" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7ff2-996b-e2e767711674_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-718a-8b49-298ec85c5ce1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7ff2-996b-e2e767711674" xlink:to="loc_dei_EntityDomain_019ef506-43b6-718a-8b49-298ec85c5ce1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-7bf0-a4d0-4ed6f70731f5" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-718a-8b49-298ec85c5ce1" xlink:to="loc_buse_EBP002Member_019ef506-43b6-7bf0-a4d0-4ed6f70731f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPRecentLegislationTextBlock_019ef506-43b6-71e4-b4e5-435b83d8e640" xlink:href="buse-20260629.xsd#buse_EBPRecentLegislationTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EbpContingencyLineItems_019ef506-43b6-7d03-971e-8ac04bd31187" xlink:to="loc_buse_EBPRecentLegislationTextBlock_019ef506-43b6-71e4-b4e5-435b83d8e640" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/ScheduleHLine4iScheduleofAssetsHeldAtEndofYear" xlink:type="simple" xlink:href="buse-20260629.xsd#ScheduleHLine4iScheduleofAssetsHeldAtEndofYear"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/ScheduleHLine4iScheduleofAssetsHeldAtEndofYear" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7d42-8af1-c3542135e71b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-76ee-ad20-dde903140763" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7d42-8af1-c3542135e71b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-76ee-ad20-dde903140763" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-709d-bdd8-01bf805c452c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-76ee-ad20-dde903140763" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-709d-bdd8-01bf805c452c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-709d-bdd8-01bf805c452c_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-709d-bdd8-01bf805c452c" xlink:to="loc_dei_EntityDomain_019ef506-43b6-709d-bdd8-01bf805c452c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-71dd-8ae7-df9aeca4cd59" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-709d-bdd8-01bf805c452c" xlink:to="loc_dei_EntityDomain_019ef506-43b6-71dd-8ae7-df9aeca4cd59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-7e51-a9b3-8ac7927ac073" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-71dd-8ae7-df9aeca4cd59" xlink:to="loc_buse_EBP002Member_019ef506-43b6-7e51-a9b3-8ac7927ac073" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTableTextBlock_019ef506-43b6-7def-8ab9-9ba2f30ea16a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7d42-8af1-c3542135e71b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTableTextBlock_019ef506-43b6-7def-8ab9-9ba2f30ea16a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/SIGNIFICANTACCOUNTINGPOLICIESPolicies" xlink:type="simple" xlink:href="buse-20260629.xsd#SIGNIFICANTACCOUNTINGPOLICIESPolicies"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/SIGNIFICANTACCOUNTINGPOLICIESPolicies" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable_019ef506-43b6-773d-8b6f-3acd179704fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable_019ef506-43b6-773d-8b6f-3acd179704fe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-7509-a862-eab92c14a2e7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable_019ef506-43b6-773d-8b6f-3acd179704fe" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-7509-a862-eab92c14a2e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7509-a862-eab92c14a2e7_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7509-a862-eab92c14a2e7" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7509-a862-eab92c14a2e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-728b-b533-6a09ce6a145f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7509-a862-eab92c14a2e7" xlink:to="loc_dei_EntityDomain_019ef506-43b6-728b-b533-6a09ce6a145f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-76f6-9415-d3d7422bc212" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-728b-b533-6a09ce6a145f" xlink:to="loc_buse_EBP002Member_019ef506-43b6-76f6-9415-d3d7422bc212" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanBasisOfAccountingPolicyTextBlock_019ef506-43b6-722e-9bb3-eeb0287a6ef4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanBasisOfAccountingPolicyTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanBasisOfAccountingPolicyTextBlock_019ef506-43b6-722e-9bb3-eeb0287a6ef4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanUseOfEstimatePolicyTextBlock_019ef506-43b6-7774-bede-320ea0d65c0c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanUseOfEstimatePolicyTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanUseOfEstimatePolicyTextBlock_019ef506-43b6-7774-bede-320ea0d65c0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentPolicyTextBlock_019ef506-43b6-7c82-a4dd-75dd3c6f4040" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentPolicyTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentPolicyTextBlock_019ef506-43b6-7c82-a4dd-75dd3c6f4040" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanPaymentToParticipantPolicyTextBlock_019ef506-43b6-76a5-be03-ad09aa78fa73" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanPaymentToParticipantPolicyTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanPaymentToParticipantPolicyTextBlock_019ef506-43b6-76a5-be03-ad09aa78fa73" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanExpensePolicyTextBlock_019ef506-43b6-71b9-b9a2-368ad69afd8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanExpensePolicyTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanExpensePolicyTextBlock_019ef506-43b6-71b9-b9a2-368ad69afd8e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPConcentrationPolicyTextBlock_019ef506-43b6-78da-900a-2d1d16c37d6d" xlink:href="buse-20260629.xsd#buse_EBPConcentrationPolicyTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:to="loc_buse_EBPConcentrationPolicyTextBlock_019ef506-43b6-78da-900a-2d1d16c37d6d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantPolicyTextBlock_019ef506-43b6-7ff6-98db-0409e25bf167" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantPolicyTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantPolicyTextBlock_019ef506-43b6-7ff6-98db-0409e25bf167" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EbpRiskAndUncertaintyPolicyTextBlock_019ef506-43b6-7297-a4b4-23a9aaf9add6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EbpRiskAndUncertaintyPolicyTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:to="loc_us-gaap-ebp_EbpRiskAndUncertaintyPolicyTextBlock_019ef506-43b6-7297-a4b4-23a9aaf9add6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanSubsequentEventPolicyTextBlock_019ef506-43b6-7af4-a0e4-25aa4e7c3330" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanSubsequentEventPolicyTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-75ef-b6c2-aaa883850a9b" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanSubsequentEventPolicyTextBlock_019ef506-43b6-7af4-a0e4-25aa4e7c3330" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/FAIRVALUEMEASUREMENTSTables" xlink:type="simple" xlink:href="buse-20260629.xsd#FAIRVALUEMEASUREMENTSTables"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/FAIRVALUEMEASUREMENTSTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems_019ef506-43b6-7b2c-a57b-87a435f7a618" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7334-957b-10e88e6b39bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems_019ef506-43b6-7b2c-a57b-87a435f7a618" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7334-957b-10e88e6b39bc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-7371-b864-5dbd62b2312c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7334-957b-10e88e6b39bc" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-7371-b864-5dbd62b2312c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7371-b864-5dbd62b2312c_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7371-b864-5dbd62b2312c" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7371-b864-5dbd62b2312c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7201-b684-8cdcc1c51744" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7371-b864-5dbd62b2312c" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7201-b684-8cdcc1c51744" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-7d92-9387-cb9759eb45ce" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-7201-b684-8cdcc1c51744" xlink:to="loc_buse_EBP002Member_019ef506-43b6-7d92-9387-cb9759eb45ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTableTextBlock_019ef506-43b6-7537-9afa-70154c9b661b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems_019ef506-43b6-7b2c-a57b-87a435f7a618" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTableTextBlock_019ef506-43b6-7537-9afa-70154c9b661b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/PARTYININTERESTTRANSACTIONSTables" xlink:type="simple" xlink:href="buse-20260629.xsd#PARTYININTERESTTRANSACTIONSTables"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/PARTYININTERESTTRANSACTIONSTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-753a-879f-c358a1eed962" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-7023-b2e8-330892a9f7b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-753a-879f-c358a1eed962" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-7023-b2e8-330892a9f7b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-78aa-89d8-9bc60d52c279" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-7023-b2e8-330892a9f7b7" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-78aa-89d8-9bc60d52c279" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-78aa-89d8-9bc60d52c279_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-78aa-89d8-9bc60d52c279" xlink:to="loc_dei_EntityDomain_019ef506-43b6-78aa-89d8-9bc60d52c279_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7c45-892d-842f51c6d826" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-78aa-89d8-9bc60d52c279" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7c45-892d-842f51c6d826" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-728e-8bc0-53255ada93b5" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-7c45-892d-842f51c6d826" xlink:to="loc_buse_EBP002Member_019ef506-43b6-728e-8bc0-53255ada93b5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTableTextBlock_019ef506-43b6-7fc4-89a1-5630019cf1fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-753a-879f-c358a1eed962" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTableTextBlock_019ef506-43b6-7fc4-89a1-5630019cf1fe" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/PLANDESCRIPTIONDetails" xlink:type="simple" xlink:href="buse-20260629.xsd#PLANDESCRIPTIONDetails"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/PLANDESCRIPTIONDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTable_019ef506-4300-7898-a75b-2e6bb6b4a6b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTable_019ef506-4300-7898-a75b-2e6bb6b4a6b0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-4300-7b41-bbf8-ac905f5375d6" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTable_019ef506-4300-7898-a75b-2e6bb6b4a6b0" xlink:to="loc_dei_LegalEntityAxis_019ef506-4300-7b41-bbf8-ac905f5375d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-4300-7b41-bbf8-ac905f5375d6_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-4300-7b41-bbf8-ac905f5375d6" xlink:to="loc_dei_EntityDomain_019ef506-4300-7b41-bbf8-ac905f5375d6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-4300-72d5-a9f7-60726b1059a2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-4300-7b41-bbf8-ac905f5375d6" xlink:to="loc_dei_EntityDomain_019ef506-4300-72d5-a9f7-60726b1059a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-4300-7979-8425-9b0156a8ef60" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-4300-72d5-a9f7-60726b1059a2" xlink:to="loc_buse_EBP002Member_019ef506-4300-7979-8425-9b0156a8ef60" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPEmployerContributionRateAxis_019ef506-4300-7bcb-a267-04bce6a82213" xlink:href="buse-20260629.xsd#buse_EBPEmployerContributionRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanTable_019ef506-4300-7898-a75b-2e6bb6b4a6b0" xlink:to="loc_buse_EBPEmployerContributionRateAxis_019ef506-4300-7bcb-a267-04bce6a82213" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPEmployerContributionRateDomain_019ef506-4300-7bcb-a267-04bce6a82213_default" xlink:href="buse-20260629.xsd#buse_EBPEmployerContributionRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_buse_EBPEmployerContributionRateAxis_019ef506-4300-7bcb-a267-04bce6a82213" xlink:to="loc_buse_EBPEmployerContributionRateDomain_019ef506-4300-7bcb-a267-04bce6a82213_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPEmployerContributionRateDomain_019ef506-4300-79de-b5ea-9703973a9195" xlink:href="buse-20260629.xsd#buse_EBPEmployerContributionRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_buse_EBPEmployerContributionRateAxis_019ef506-4300-7bcb-a267-04bce6a82213" xlink:to="loc_buse_EBPEmployerContributionRateDomain_019ef506-4300-79de-b5ea-9703973a9195" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_FirstThreePercentMember_019ef506-4300-7786-afe4-5fca42c63121" xlink:href="buse-20260629.xsd#buse_FirstThreePercentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_buse_EBPEmployerContributionRateDomain_019ef506-4300-79de-b5ea-9703973a9195" xlink:to="loc_buse_FirstThreePercentMember_019ef506-4300-7786-afe4-5fca42c63121" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_NextTwoPercentMember_019ef506-4300-7834-ae58-00142465d0ca" xlink:href="buse-20260629.xsd#buse_NextTwoPercentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_buse_EBPEmployerContributionRateDomain_019ef506-4300-79de-b5ea-9703973a9195" xlink:to="loc_buse_NextTwoPercentMember_019ef506-4300-7834-ae58-00142465d0ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPParticipantMinimumAge_019ef506-4300-73d4-9322-ab272999c661" xlink:href="buse-20260629.xsd#buse_EBPParticipantMinimumAge"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_buse_EBPParticipantMinimumAge_019ef506-4300-73d4-9322-ab272999c661" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPRequisiteServicePeriod_019ef506-4300-7780-a30e-96b9362b5a07" xlink:href="buse-20260629.xsd#buse_EBPRequisiteServicePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_buse_EBPRequisiteServicePeriod_019ef506-4300-7780-a30e-96b9362b5a07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPRequisiteServiceTime_019ef506-4300-72a6-9ed7-1e62550b94b9" xlink:href="buse-20260629.xsd#buse_EBPRequisiteServiceTime"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_buse_EBPRequisiteServiceTime_019ef506-4300-72a6-9ed7-1e62550b94b9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerContributionParticipantCompensationMatchedPercentage_019ef506-4300-718b-bebf-5bb14b6fd44b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanEmployerContributionParticipantCompensationMatchedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerContributionParticipantCompensationMatchedPercentage_019ef506-4300-718b-bebf-5bb14b6fd44b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerContributionMatchingPercentage_019ef506-4300-7788-9ebf-d15f41c52e3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanEmployerContributionMatchingPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerContributionMatchingPercentage_019ef506-4300-7788-9ebf-d15f41c52e3e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPEmployerSharingContributionOfEligibleCompensation_019ef506-4300-7f51-bef8-26940cefd149" xlink:href="buse-20260629.xsd#buse_EBPEmployerSharingContributionOfEligibleCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_buse_EBPEmployerSharingContributionOfEligibleCompensation_019ef506-4300-7f51-bef8-26940cefd149" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPEmployerContributionVestingPercentage_019ef506-4300-7194-adfe-bd8c5a5547c9" xlink:href="buse-20260629.xsd#buse_EBPEmployerContributionVestingPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_buse_EBPEmployerContributionVestingPercentage_019ef506-4300-7194-adfe-bd8c5a5547c9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPEmployerContributionVestingServicePeriod_019ef506-4300-7ec2-aca8-e4d4009d43bf" xlink:href="buse-20260629.xsd#buse_EBPEmployerContributionVestingServicePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_buse_EBPEmployerContributionVestingServicePeriod_019ef506-4300-7ec2-aca8-e4d4009d43bf" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingAmount_019ef506-4300-7844-9977-76aa5b738d16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingAmount_019ef506-4300-7844-9977-76aa5b738d16" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingToTotalAccountPercentage_019ef506-4300-7c4d-9956-e06fd42a64af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingToTotalAccountPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingToTotalAccountPercentage_019ef506-4300-7c4d-9956-e06fd42a64af" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate_019ef506-4300-7db1-bb22-b2591329d86f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate_019ef506-4300-7db1-bb22-b2591329d86f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPNoteReceivableFromParticipantMaximumNumberOfLoansOutstanding_019ef506-4300-748f-8387-95f29eeac11f" xlink:href="buse-20260629.xsd#buse_EBPNoteReceivableFromParticipantMaximumNumberOfLoansOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_buse_EBPNoteReceivableFromParticipantMaximumNumberOfLoansOutstanding_019ef506-4300-748f-8387-95f29eeac11f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPNoteReceivableFromParticipantGeneralLoanMaximumBorrowingTerm_019ef506-4300-7b6c-8cfa-afe1bdcfc9c7" xlink:href="buse-20260629.xsd#buse_EBPNoteReceivableFromParticipantGeneralLoanMaximumBorrowingTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_buse_EBPNoteReceivableFromParticipantGeneralLoanMaximumBorrowingTerm_019ef506-4300-7b6c-8cfa-afe1bdcfc9c7" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPNoteReceivableFromParticipantAccountPrimaryResidenceMaximumBorrowingTerm_019ef506-4300-7699-a4ef-4243140bd75b" xlink:href="buse-20260629.xsd#buse_EBPNoteReceivableFromParticipantAccountPrimaryResidenceMaximumBorrowingTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_buse_EBPNoteReceivableFromParticipantAccountPrimaryResidenceMaximumBorrowingTerm_019ef506-4300-7699-a4ef-4243140bd75b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPInvoluntaryCashOutLimit_019ef506-4300-76cf-a51a-87a9ab132b4d" xlink:href="buse-20260629.xsd#buse_EBPInvoluntaryCashOutLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_buse_EBPInvoluntaryCashOutLimit_019ef506-4300-76cf-a51a-87a9ab132b4d" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccountDecreaseForAdministrativeExpense_019ef506-4300-708d-905f-19d55278ef0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccountDecreaseForAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccountDecreaseForAdministrativeExpense_019ef506-4300-708d-905f-19d55278ef0a" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccount_019ef506-4300-77ce-ac0b-16ff44fc4251" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems_019ef506-4300-7b9a-a250-d72e66a32686" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccount_019ef506-4300-77ce-ac0b-16ff44fc4251" xlink:type="arc" order="16"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/SIGNIFICANTACCOUNTINGPOLICIESDetails" xlink:type="simple" xlink:href="buse-20260629.xsd#SIGNIFICANTACCOUNTINGPOLICIESDetails"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/SIGNIFICANTACCOUNTINGPOLICIESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-77e6-bdc2-8b34164e7e40" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable_019ef506-43b6-7ac0-9328-50c89fbf8f5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-77e6-bdc2-8b34164e7e40" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable_019ef506-43b6-7ac0-9328-50c89fbf8f5b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-78e7-887c-8e36e648d103" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable_019ef506-43b6-7ac0-9328-50c89fbf8f5b" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-78e7-887c-8e36e648d103" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-78e7-887c-8e36e648d103_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-78e7-887c-8e36e648d103" xlink:to="loc_dei_EntityDomain_019ef506-43b6-78e7-887c-8e36e648d103_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7d6a-ad05-46cfb8729af3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-78e7-887c-8e36e648d103" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7d6a-ad05-46cfb8729af3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-7575-91e8-1805a572715f" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-7d6a-ad05-46cfb8729af3" xlink:to="loc_buse_EBP002Member_019ef506-43b6-7575-91e8-1805a572715f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7411-a962-5dc9268a3074" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyTable_019ef506-43b6-7ac0-9328-50c89fbf8f5b" xlink:to="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7411-a962-5dc9268a3074" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7411-a962-5dc9268a3074_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7411-a962-5dc9268a3074" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7411-a962-5dc9268a3074_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7216-973f-963a303cb9db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7411-a962-5dc9268a3074" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7216-973f-963a303cb9db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerCommonStockMember_019ef506-43b6-7239-892c-c0fe399a29b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanEmployerCommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7216-973f-963a303cb9db" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerCommonStockMember_019ef506-43b6-7239-892c-c0fe399a29b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EbpRiskAndUncertaintyConcentrationOfInvestmentAtFairValueToTotalInvestmentsPercentage_019ef506-43b6-7f96-b055-f6456b49cd70" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EbpRiskAndUncertaintyConcentrationOfInvestmentAtFairValueToTotalInvestmentsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-77e6-bdc2-8b34164e7e40" xlink:to="loc_us-gaap-ebp_EbpRiskAndUncertaintyConcentrationOfInvestmentAtFairValueToTotalInvestmentsPercentage_019ef506-43b6-7f96-b055-f6456b49cd70" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAllowanceForCreditLoss_019ef506-43b6-7ef9-b104-0309bf452bef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanAccountingPolicyLineItems_019ef506-43b6-77e6-bdc2-8b34164e7e40" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAllowanceForCreditLoss_019ef506-43b6-7ef9-b104-0309bf452bef" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/FAIRVALUEMEASUREMENTSDetails" xlink:type="simple" xlink:href="buse-20260629.xsd#FAIRVALUEMEASUREMENTSDetails"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/FAIRVALUEMEASUREMENTSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems_019ef506-43b6-7d9c-ab28-e212eee8154e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7e8e-84e7-b86ca27da636" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems_019ef506-43b6-7d9c-ab28-e212eee8154e" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7e8e-84e7-b86ca27da636" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-7919-acc6-091822904e8f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7e8e-84e7-b86ca27da636" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-7919-acc6-091822904e8f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7919-acc6-091822904e8f_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7919-acc6-091822904e8f" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7919-acc6-091822904e8f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-75c0-ac1b-52ce42e91408" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7919-acc6-091822904e8f" xlink:to="loc_dei_EntityDomain_019ef506-43b6-75c0-ac1b-52ce42e91408" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-7e32-ba6b-f2b8e29bf0b5" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-75c0-ac1b-52ce42e91408" xlink:to="loc_buse_EBP002Member_019ef506-43b6-7e32-ba6b-f2b8e29bf0b5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019ef506-43b6-7225-a5ee-ff565cbc0a84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7e8e-84e7-b86ca27da636" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019ef506-43b6-7225-a5ee-ff565cbc0a84" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ef506-43b6-7225-a5ee-ff565cbc0a84_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019ef506-43b6-7225-a5ee-ff565cbc0a84" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ef506-43b6-7225-a5ee-ff565cbc0a84_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ef506-43b6-7262-adb9-a8a0f2fe39c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019ef506-43b6-7225-a5ee-ff565cbc0a84" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ef506-43b6-7262-adb9-a8a0f2fe39c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel12And3Member_019ef506-43b6-7242-810f-ef7a2b4003fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel12And3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019ef506-43b6-7262-adb9-a8a0f2fe39c2" xlink:to="loc_us-gaap_FairValueInputsLevel12And3Member_019ef506-43b6-7242-810f-ef7a2b4003fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019ef506-43b6-7bf8-9e28-7e4dcafb683c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInputsLevel12And3Member_019ef506-43b6-7242-810f-ef7a2b4003fc" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019ef506-43b6-7bf8-9e28-7e4dcafb683c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019ef506-43b6-7c56-88ee-aaa3c10a0c50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInputsLevel12And3Member_019ef506-43b6-7242-810f-ef7a2b4003fc" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019ef506-43b6-7c56-88ee-aaa3c10a0c50" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019ef506-43b6-7b39-9961-67038d83a622" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInputsLevel12And3Member_019ef506-43b6-7242-810f-ef7a2b4003fc" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019ef506-43b6-7b39-9961-67038d83a622" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7b23-8708-5d0c338af856" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavTable_019ef506-43b6-7e8e-84e7-b86ca27da636" xlink:to="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7b23-8708-5d0c338af856" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7b23-8708-5d0c338af856_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7b23-8708-5d0c338af856" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7b23-8708-5d0c338af856_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7cae-b202-8f173e1dd458" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7b23-8708-5d0c338af856" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7cae-b202-8f173e1dd458" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MutualFundMember_019ef506-43b6-7acd-9ff7-5d87485c982d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MutualFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7cae-b202-8f173e1dd458" xlink:to="loc_us-gaap_MutualFundMember_019ef506-43b6-7acd-9ff7-5d87485c982d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_ManagedFundsMember_019ef506-43b6-77d4-88f0-660f40389b97" xlink:href="buse-20260629.xsd#buse_ManagedFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7cae-b202-8f173e1dd458" xlink:to="loc_buse_ManagedFundsMember_019ef506-43b6-77d4-88f0-660f40389b97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPEmployerCommonStockAndStockFundMember_019ef506-43b6-7a47-85f9-9f1b7020d5b3" xlink:href="buse-20260629.xsd#buse_EBPEmployerCommonStockAndStockFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7cae-b202-8f173e1dd458" xlink:to="loc_buse_EBPEmployerCommonStockAndStockFundMember_019ef506-43b6-7a47-85f9-9f1b7020d5b3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_019ef506-43b6-7a48-a531-b2dda94de0ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7cae-b202-8f173e1dd458" xlink:to="loc_us-gaap_MoneyMarketFundsMember_019ef506-43b6-7a48-a531-b2dda94de0ba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentExcludingPlanInterestInMasterTrustFairValue_019ef506-43b6-79c7-936f-7eb0ca648fdc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentExcludingPlanInterestInMasterTrustFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentFairValueAndNavLineItems_019ef506-43b6-7d9c-ab28-e212eee8154e" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentExcludingPlanInterestInMasterTrustFairValue_019ef506-43b6-79c7-936f-7eb0ca648fdc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/PARTYININTERESTTRANSACTIONSDetails" xlink:type="simple" xlink:href="buse-20260629.xsd#PARTYININTERESTTRANSACTIONSDetails"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/PARTYININTERESTTRANSACTIONSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-7c13-88e0-c49dfe27aefe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-711d-ad5f-9acc98663cf3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-7c13-88e0-c49dfe27aefe" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-711d-ad5f-9acc98663cf3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-7f8c-989f-90fd183012ca" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-711d-ad5f-9acc98663cf3" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-7f8c-989f-90fd183012ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7f8c-989f-90fd183012ca_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7f8c-989f-90fd183012ca" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7f8c-989f-90fd183012ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7206-950f-d9826b056ce3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-7f8c-989f-90fd183012ca" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7206-950f-d9826b056ce3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-7add-b651-c1ec73440c4a" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-7206-950f-d9826b056ce3" xlink:to="loc_buse_EBP002Member_019ef506-43b6-7add-b651-c1ec73440c4a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7099-ae51-6d9a4f988d0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-711d-ad5f-9acc98663cf3" xlink:to="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7099-ae51-6d9a4f988d0b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7099-ae51-6d9a4f988d0b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7099-ae51-6d9a4f988d0b" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7099-ae51-6d9a4f988d0b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-77cf-b32d-b243ecc41fe2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7099-ae51-6d9a4f988d0b" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-77cf-b32d-b243ecc41fe2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPCashMember_019ef506-43b6-7db4-9075-899d097429cc" xlink:href="buse-20260629.xsd#buse_EBPCashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-77cf-b32d-b243ecc41fe2" xlink:to="loc_buse_EBPCashMember_019ef506-43b6-7db4-9075-899d097429cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_019ef506-43b6-7138-9805-274e8bfca8ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-77cf-b32d-b243ecc41fe2" xlink:to="loc_us-gaap_MoneyMarketFundsMember_019ef506-43b6-7138-9805-274e8bfca8ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerCommonStockMember_019ef506-43b6-7c2e-85b7-a2d26bcbea06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanEmployerCommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-77cf-b32d-b243ecc41fe2" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerCommonStockMember_019ef506-43b6-7c2e-85b7-a2d26bcbea06" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerCommonStockFundMember_019ef506-43b6-7eb4-b26e-4bd07c03d967" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanEmployerCommonStockFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-77cf-b32d-b243ecc41fe2" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanEmployerCommonStockFundMember_019ef506-43b6-7eb4-b26e-4bd07c03d967" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_ManagedFundsMember_019ef506-43b6-7ad4-a319-b19e5afab8ea" xlink:href="buse-20260629.xsd#buse_ManagedFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-77cf-b32d-b243ecc41fe2" xlink:to="loc_buse_ManagedFundsMember_019ef506-43b6-7ad4-a319-b19e5afab8ea" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestAxis_019ef506-43b6-7e47-8ed4-c2363b8017a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsTable_019ef506-43b6-711d-ad5f-9acc98663cf3" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestAxis_019ef506-43b6-7e47-8ed4-c2363b8017a1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestDomain_019ef506-43b6-7e47-8ed4-c2363b8017a1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestAxis_019ef506-43b6-7e47-8ed4-c2363b8017a1" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestDomain_019ef506-43b6-7e47-8ed4-c2363b8017a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestDomain_019ef506-43b6-70cb-94c5-e27b09b7c59d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestAxis_019ef506-43b6-7e47-8ed4-c2363b8017a1" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestDomain_019ef506-43b6-70cb-94c5-e27b09b7c59d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanTrusteeMember_019ef506-43b6-709d-b5e0-4e462f591981" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanTrusteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestDomain_019ef506-43b6-70cb-94c5-e27b09b7c59d" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanTrusteeMember_019ef506-43b6-709d-b5e0-4e462f591981" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPEmployerMember_019ef506-43b6-7f08-a15b-6394ff930d94" xlink:href="buse-20260629.xsd#buse_EBPEmployerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestDomain_019ef506-43b6-70cb-94c5-e27b09b7c59d" xlink:to="loc_buse_EBPEmployerMember_019ef506-43b6-7f08-a15b-6394ff930d94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanCash_019ef506-43b6-7bd1-8545-271a71a1ea37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-7c13-88e0-c49dfe27aefe" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanCash_019ef506-43b6-7bd1-8545-271a71a1ea37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentExcludingPlanInterestInMasterTrustFairValue_019ef506-43b6-77c9-bfe6-9d36b65adaec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanInvestmentExcludingPlanInterestInMasterTrustFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-7c13-88e0-c49dfe27aefe" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanInvestmentExcludingPlanInterestInMasterTrustFairValue_019ef506-43b6-77c9-bfe6-9d36b65adaec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipant_019ef506-43b6-7f67-85ad-16f0643c9c76" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanRelatedPartyAndPartyInInterestTransactionsLineItems_019ef506-43b6-7c13-88e0-c49dfe27aefe" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipant_019ef506-43b6-7f67-85ad-16f0643c9c76" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/ScheduleHLine4iScheduleofAssetsHeldAtEndofYearDetails" xlink:type="simple" xlink:href="buse-20260629.xsd#ScheduleHLine4iScheduleofAssetsHeldAtEndofYearDetails"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/ScheduleHLine4iScheduleofAssetsHeldAtEndofYearDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-764e-99a4-cf6897bf5498" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-764e-99a4-cf6897bf5498" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-764e-99a4-cf6897bf5498_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-764e-99a4-cf6897bf5498" xlink:to="loc_dei_EntityDomain_019ef506-43b6-764e-99a4-cf6897bf5498_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7f8d-9b43-9e2757d468ec" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-764e-99a4-cf6897bf5498" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7f8d-9b43-9e2757d468ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-75b0-ac6d-a83676029be5" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-7f8d-9b43-9e2757d468ec" xlink:to="loc_buse_EBP002Member_019ef506-43b6-75b0-ac6d-a83676029be5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIdentifierAxis_019ef506-43b6-7d5f-aa19-b265bb6a74ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentIdentifierAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:to="loc_us-gaap_InvestmentIdentifierAxis_019ef506-43b6-7d5f-aa19-b265bb6a74ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7ca6-8fb8-80e65c65035b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:to="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7ca6-8fb8-80e65c65035b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7ca6-8fb8-80e65c65035b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7ca6-8fb8-80e65c65035b" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7ca6-8fb8-80e65c65035b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-71eb-ad6a-efe24be26e02" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7ca6-8fb8-80e65c65035b" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-71eb-ad6a-efe24be26e02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPEmployerCommonStockAndStockFundMember_019ef506-43b6-7c98-8f4e-3d7f9c61852d" xlink:href="buse-20260629.xsd#buse_EBPEmployerCommonStockAndStockFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-71eb-ad6a-efe24be26e02" xlink:to="loc_buse_EBPEmployerCommonStockAndStockFundMember_019ef506-43b6-7c98-8f4e-3d7f9c61852d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MutualFundMember_019ef506-43b6-7406-acd1-6d002d0e15c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MutualFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-71eb-ad6a-efe24be26e02" xlink:to="loc_us-gaap_MutualFundMember_019ef506-43b6-7406-acd1-6d002d0e15c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_ManagedFundsMember_019ef506-43b6-73f4-bfed-088303a03f25" xlink:href="buse-20260629.xsd#buse_ManagedFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-71eb-ad6a-efe24be26e02" xlink:to="loc_buse_ManagedFundsMember_019ef506-43b6-73f4-bfed-088303a03f25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019ef506-43b6-7430-a7b5-21e7d12284f5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:to="loc_srt_RangeAxis_019ef506-43b6-7430-a7b5-21e7d12284f5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ef506-43b6-7430-a7b5-21e7d12284f5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019ef506-43b6-7430-a7b5-21e7d12284f5" xlink:to="loc_srt_RangeMember_019ef506-43b6-7430-a7b5-21e7d12284f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ef506-43b6-75d9-b445-4f1d850a5630" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019ef506-43b6-7430-a7b5-21e7d12284f5" xlink:to="loc_srt_RangeMember_019ef506-43b6-75d9-b445-4f1d850a5630" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019ef506-43b6-73ab-90a8-e753012e2d2d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ef506-43b6-75d9-b445-4f1d850a5630" xlink:to="loc_srt_MinimumMember_019ef506-43b6-73ab-90a8-e753012e2d2d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019ef506-43b6-72d7-aec2-baea54fe2770" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ef506-43b6-75d9-b445-4f1d850a5630" xlink:to="loc_srt_MaximumMember_019ef506-43b6-72d7-aec2-baea54fe2770" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019ef506-43b6-7abd-8cd4-8594363728a6" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_dei_EntityTaxIdentificationNumber_019ef506-43b6-7abd-8cd4-8594363728a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanPlanNumber_019ef506-43b6-77d9-90e9-f3407cfb6ff1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanPlanNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanPlanNumber_019ef506-43b6-77d9-90e9-f3407cfb6ff1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentInvestmentExcludingPlanInterestInMasterTrustCurrentValue_019ef506-43b6-7c9b-9829-1e6a5f900761" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentInvestmentExcludingPlanInterestInMasterTrustCurrentValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentInvestmentExcludingPlanInterestInMasterTrustCurrentValue_019ef506-43b6-7c9b-9829-1e6a5f900761" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentParticipantLoanAfterDeemedDistribution_019ef506-43b6-7eab-b2d1-28162b326a88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentParticipantLoanAfterDeemedDistribution"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentParticipantLoanAfterDeemedDistribution_019ef506-43b6-7eab-b2d1-28162b326a88" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestment_019ef506-43b6-7628-a7b2-c24dab984ae5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestment_019ef506-43b6-7628-a7b2-c24dab984ae5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate_019ef506-43b6-7856-918f-6306966a4d36" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate_019ef506-43b6-7856-918f-6306966a4d36" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.busey.com/role/ScheduleHLine4iScheduleofAssetsHeldAtEndofYearDetails_1" xlink:type="simple" xlink:href="buse-20260629.xsd#ScheduleHLine4iScheduleofAssetsHeldAtEndofYearDetails_1"/>
  <link:definitionLink xlink:role="http://www.busey.com/role/ScheduleHLine4iScheduleofAssetsHeldAtEndofYearDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019ef506-43b6-764e-99a4-cf6897bf5498" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:to="loc_dei_LegalEntityAxis_019ef506-43b6-764e-99a4-cf6897bf5498" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-764e-99a4-cf6897bf5498_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-764e-99a4-cf6897bf5498" xlink:to="loc_dei_EntityDomain_019ef506-43b6-764e-99a4-cf6897bf5498_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019ef506-43b6-7f8d-9b43-9e2757d468ec" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019ef506-43b6-764e-99a4-cf6897bf5498" xlink:to="loc_dei_EntityDomain_019ef506-43b6-7f8d-9b43-9e2757d468ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBP002Member_019ef506-43b6-75b0-ac6d-a83676029be5" xlink:href="buse-20260629.xsd#buse_EBP002Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019ef506-43b6-7f8d-9b43-9e2757d468ec" xlink:to="loc_buse_EBP002Member_019ef506-43b6-75b0-ac6d-a83676029be5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7ca6-8fb8-80e65c65035b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:to="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7ca6-8fb8-80e65c65035b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7ca6-8fb8-80e65c65035b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7ca6-8fb8-80e65c65035b" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-7ca6-8fb8-80e65c65035b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-71eb-ad6a-efe24be26e02" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019ef506-43b6-7ca6-8fb8-80e65c65035b" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-71eb-ad6a-efe24be26e02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_EBPEmployerCommonStockAndStockFundMember_019ef506-43b6-7c98-8f4e-3d7f9c61852d" xlink:href="buse-20260629.xsd#buse_EBPEmployerCommonStockAndStockFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-71eb-ad6a-efe24be26e02" xlink:to="loc_buse_EBPEmployerCommonStockAndStockFundMember_019ef506-43b6-7c98-8f4e-3d7f9c61852d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MutualFundMember_019ef506-43b6-7406-acd1-6d002d0e15c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MutualFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-71eb-ad6a-efe24be26e02" xlink:to="loc_us-gaap_MutualFundMember_019ef506-43b6-7406-acd1-6d002d0e15c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_buse_ManagedFundsMember_019ef506-43b6-73f4-bfed-088303a03f25" xlink:href="buse-20260629.xsd#buse_ManagedFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019ef506-43b6-71eb-ad6a-efe24be26e02" xlink:to="loc_buse_ManagedFundsMember_019ef506-43b6-73f4-bfed-088303a03f25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019ef506-43b6-7430-a7b5-21e7d12284f5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentTable_019ef506-43b6-78a6-8f90-b0d60e47ad26" xlink:to="loc_srt_RangeAxis_019ef506-43b6-7430-a7b5-21e7d12284f5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ef506-43b6-7430-a7b5-21e7d12284f5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019ef506-43b6-7430-a7b5-21e7d12284f5" xlink:to="loc_srt_RangeMember_019ef506-43b6-7430-a7b5-21e7d12284f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019ef506-43b6-75d9-b445-4f1d850a5630" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019ef506-43b6-7430-a7b5-21e7d12284f5" xlink:to="loc_srt_RangeMember_019ef506-43b6-75d9-b445-4f1d850a5630" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019ef506-43b6-73ab-90a8-e753012e2d2d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ef506-43b6-75d9-b445-4f1d850a5630" xlink:to="loc_srt_MinimumMember_019ef506-43b6-73ab-90a8-e753012e2d2d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019ef506-43b6-72d7-aec2-baea54fe2770" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019ef506-43b6-75d9-b445-4f1d850a5630" xlink:to="loc_srt_MaximumMember_019ef506-43b6-72d7-aec2-baea54fe2770" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019ef506-43b6-7abd-8cd4-8594363728a6" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_dei_EntityTaxIdentificationNumber_019ef506-43b6-7abd-8cd4-8594363728a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanPlanNumber_019ef506-43b6-77d9-90e9-f3407cfb6ff1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanPlanNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanPlanNumber_019ef506-43b6-77d9-90e9-f3407cfb6ff1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentInvestmentExcludingPlanInterestInMasterTrustCurrentValue_019ef506-43b6-7c9b-9829-1e6a5f900761" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentInvestmentExcludingPlanInterestInMasterTrustCurrentValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentInvestmentExcludingPlanInterestInMasterTrustCurrentValue_019ef506-43b6-7c9b-9829-1e6a5f900761" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentParticipantLoanAfterDeemedDistribution_019ef506-43b6-7eab-b2d1-28162b326a88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentParticipantLoanAfterDeemedDistribution"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestmentParticipantLoanAfterDeemedDistribution_019ef506-43b6-7eab-b2d1-28162b326a88" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestment_019ef506-43b6-7628-a7b2-c24dab984ae5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanAssetHeldForInvestment_019ef506-43b6-7628-a7b2-c24dab984ae5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate_019ef506-43b6-7856-918f-6306966a4d36" xlink:href="https://xbrl.fasb.org/us-gaap/2026/ebp/elts/us-gaap-ebp-2026.xsd#us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap-ebp_EmployeeBenefitPlanScheduleOfAssetHeldForInvestmentLineItems_019ef506-43b6-7178-b29f-1ee2ac8a4133" xlink:to="loc_us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate_019ef506-43b6-7856-918f-6306966a4d36" xlink:type="arc" order="5"/>
  </link:definitionLink>
</link:linkbase>
