questionable

adjective

1 it is questionable whether such an attack could be effective | he indulges in jokes of questionable taste:

controversial, contentious, open to question, open to doubt, in doubt, doubtful, dubious, uncertain, unsure, debatable, in dispute, in question, arguable, problematic, problematical;

unverified, unprovable, unresolved, unsettled, undecided, equivocal, unconvincing, implausible, improbable, not definite, unclear, not obvious, apocryphal, spurious, borderline, marginal, moot;

informal iffy;

British, informal dodgy.

▷antonyms certain, indisputable.

2 some of his questionable financial dealings have been investigated:

suspicious, suspect, under suspicion, irregular, dubious, doubtful, odd, strange, not quite right, mysterious, murky, dark, shifty, unsavoury, disreputable, potentially dishonest, potentially illegal;

informal funny, fishy, shady, iffy;

British, informal dodgy.

questionable Oxford Dictionary of English