in question is an adjective meaning "open to doubt or suspicion". It carries one recorded sense.
open to doubt or suspicion
“the candidate's doubtful past”
“he has a dubious record indeed”
“what one found uncertain the other found dubious or downright false”
“it was more than dubitable whether the friend was as influential as she thought”
Definitions, synonyms and semantic relations for in question come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.