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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019d5484-1e6c-71c8-8dd6-0db27bae2993,g:89fc25d4-267b-4e6d-9148-c3c64a1ce843-->
<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://xbrl.sec.gov/ecd/role/PvpAdjustmentsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#PvpAdjustmentsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/PvpAdjustmentsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllAdjToCompMember" xlink:href="https://xbrl.sec.gov/ecd/2026/ecd-2026.xsd#ecd_AllAdjToCompMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_band_IncreaseBasedOnIncrementalFairValueOfOptionsSARsMember_019d5484-1e6c-7d03-a924-26cd0eccf251" xlink:href="band-20260414.xsd#band_IncreaseBasedOnIncrementalFairValueOfOptionsSARsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="loc_band_IncreaseBasedOnIncrementalFairValueOfOptionsSARsMember_019d5484-1e6c-7d03-a924-26cd0eccf251" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_band_DeductionForChangeInTheActuarialPresentValuesReportedUnderTheChangeInPensionValueAndNonqualifiedDeferredCompensationEarningsMember_019d5484-1e6c-7dee-88fd-34916fea39f3" xlink:href="band-20260414.xsd#band_DeductionForChangeInTheActuarialPresentValuesReportedUnderTheChangeInPensionValueAndNonqualifiedDeferredCompensationEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="loc_band_DeductionForChangeInTheActuarialPresentValuesReportedUnderTheChangeInPensionValueAndNonqualifiedDeferredCompensationEarningsMember_019d5484-1e6c-7dee-88fd-34916fea39f3" xlink:type="arc" order="5"/>
  </link:definitionLink>
</link:linkbase>