Synonyms for In question:

adj.

fallible (adjective)
questionable.
open (adjective)
dubitable, doubtful, dubious.
problematical (adjective)
at issue.

n.

in question (noun)
doubtful, at issue, relevant, dubious, in dispute, in hand, under consideration, dubitable, questionable.

Other synonyms:

adj.
dubitable.
n.
at issue.