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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:01a019d6-e729-7f7a-87f2-42637111232a,g:d5c41c6c-5690-45d6-ba91-8ba1199038d8-->
<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.cycurion.com/role/Cover" xlink:type="simple" xlink:href="cycu-20260817.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.cycurion.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_01a019d6-e729-7dc0-ad24-1a5d97be5270" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_DocumentInformationTable_01a019d6-e729-7dc0-ad24-1a5d97be5270" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_01a019d6-e729-796f-a8fe-15436591dbb6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_01a019d6-e729-7dc0-ad24-1a5d97be5270" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_01a019d6-e729-796f-a8fe-15436591dbb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a019d6-e729-796f-a8fe-15436591dbb6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_01a019d6-e729-796f-a8fe-15436591dbb6" xlink:to="loc_us-gaap_EquityComponentDomain_01a019d6-e729-796f-a8fe-15436591dbb6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_01a019d6-e729-74cb-a172-bb75fe2ecd09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_01a019d6-e729-796f-a8fe-15436591dbb6" xlink:to="loc_us-gaap_EquityComponentDomain_01a019d6-e729-74cb-a172-bb75fe2ecd09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_01a019d6-e729-75db-a58f-e9db37bd93aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a019d6-e729-74cb-a172-bb75fe2ecd09" xlink:to="loc_us-gaap_CommonStockMember_01a019d6-e729-75db-a58f-e9db37bd93aa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantMember_01a019d6-e729-75fd-9fa6-8fb63339a329" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WarrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_01a019d6-e729-74cb-a172-bb75fe2ecd09" xlink:to="loc_us-gaap_WarrantMember_01a019d6-e729-75fd-9fa6-8fb63339a329" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_01a019d6-e729-794c-a6f2-548803b3587a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_DocumentType_01a019d6-e729-794c-a6f2-548803b3587a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_01a019d6-e729-72c0-9f52-09dfc03c39c9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_DocumentPeriodEndDate_01a019d6-e729-72c0-9f52-09dfc03c39c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_01a019d6-e729-73d6-a014-259f7756f0d6" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityRegistrantName_01a019d6-e729-73d6-a014-259f7756f0d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_01a019d6-e729-7ba0-ba01-7f86c1ab3b91" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityIncorporationStateCountryCode_01a019d6-e729-7ba0-ba01-7f86c1ab3b91" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_01a019d6-e729-726a-a94d-939ed971829a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityFileNumber_01a019d6-e729-726a-a94d-939ed971829a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_01a019d6-e729-7771-9e53-386675032de4" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityTaxIdentificationNumber_01a019d6-e729-7771-9e53-386675032de4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_01a019d6-e729-784e-83dc-565576c3453d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityAddressAddressLine1_01a019d6-e729-784e-83dc-565576c3453d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_01a019d6-e729-7a7d-93e6-2b71938b45d5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityAddressAddressLine2_01a019d6-e729-7a7d-93e6-2b71938b45d5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_01a019d6-e729-7194-82fd-957719c3e0a8" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityAddressCityOrTown_01a019d6-e729-7194-82fd-957719c3e0a8" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_01a019d6-e729-7ba0-9827-6577894a4daa" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityAddressStateOrProvince_01a019d6-e729-7ba0-9827-6577894a4daa" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_01a019d6-e729-7e50-89bd-6efad6512501" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityAddressPostalZipCode_01a019d6-e729-7e50-89bd-6efad6512501" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_01a019d6-e729-7cf7-a50e-9768cf737fb3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_CityAreaCode_01a019d6-e729-7cf7-a50e-9768cf737fb3" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_01a019d6-e729-7ade-81b0-81e50c854dc9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_LocalPhoneNumber_01a019d6-e729-7ade-81b0-81e50c854dc9" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_01a019d6-e729-7626-83fa-d19d43763acb" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_WrittenCommunications_01a019d6-e729-7626-83fa-d19d43763acb" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_01a019d6-e729-738c-a58e-f0680ee7d0e3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_SolicitingMaterial_01a019d6-e729-738c-a58e-f0680ee7d0e3" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_01a019d6-e729-71ed-8c1a-86f54820bef7" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_PreCommencementTenderOffer_01a019d6-e729-71ed-8c1a-86f54820bef7" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_01a019d6-e729-7bf3-8cd4-85efe9caeaf3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_01a019d6-e729-7bf3-8cd4-85efe9caeaf3" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_01a019d6-e729-7b62-a1db-e37b6187cca3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_Security12bTitle_01a019d6-e729-7b62-a1db-e37b6187cca3" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_01a019d6-e729-7498-8c60-9a4dcfdd585f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_TradingSymbol_01a019d6-e729-7498-8c60-9a4dcfdd585f" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_01a019d6-e729-7cf0-904d-34321ec339b3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_SecurityExchangeName_01a019d6-e729-7cf0-904d-34321ec339b3" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_01a019d6-e729-731f-8305-540e12da424e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityEmergingGrowthCompany_01a019d6-e729-731f-8305-540e12da424e" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityExTransitionPeriod_01a019d6-e729-7181-8f33-60c6ad24b5a0" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityExTransitionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityExTransitionPeriod_01a019d6-e729-7181-8f33-60c6ad24b5a0" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_01a019d6-e729-75c8-8595-de414e135f78" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_EntityCentralIndexKey_01a019d6-e729-75c8-8595-de414e135f78" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_01a019d6-e729-73c6-9f0d-352633a865a5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_01a019d6-e729-7ebe-8d4f-032cf582a4c6" xlink:to="loc_dei_AmendmentFlag_01a019d6-e729-73c6-9f0d-352633a865a5" xlink:type="arc" order="23"/>
  </link:definitionLink>
</link:linkbase>
