Sorry for reverting late, was not well and couldnt work on this earlier.
Please find groovy script below which i tried, it says 0. Can you please help fixing the namespace for the response posted in original query.
def groovyUtils = new com.eviware.soapui.support.GroovyUtils( context )
def requsetHolder = groovyUtils.getXmlHolder( "Define - Request#Request")
def responseHolder = groovyUtils.getXmlHolder("Define - Request#Response")
log.info(responseHolder.getPrettyXml())
// define namespace
responseHolder.namespaces["ns1"] = "http://services.aonaware.com/webservices/"
responseHolder.namespaces["soap"] = "http://schemas.xmlsoap.org/soap/envelope/"
log.info(responseHolder["count(//WordDefinition)"])