- questionable - subject to question; "questionable motives"; "a questionable reputation"; "a fire of questionable origin"
Antonyms: unquestionable, acknowledged, beyond doubt, indubitable, for sure, mathematical, unchallengeable, unchallenged, undisputed, undoubted, unquestioned, unimpeachable
- questionable, refutable, confutable, confutative - able to be refuted
Antonym: undeniable (indirect, via deniable)