Adjective doubtful, uncertain
Synonyms: ambiguous, apocryphal, arguable, contingent, controversial, controvertible, cryptic, debatable, disputable, dubious, dubitable, enigmatic, equivocal, fishy, hard to believe, hypothetical, iffy, indecisive, indefinite, indeterminate, moot, mysterious, obscure, occult, open to doubt, open to question, oracular, paradoxical, problematic, problematical, provisional, shady, suspect, suspicious, unconfirmed, undefined, under advisement, under examination, unproven, unreliable, unsettled, vague
Antonyms: certain, definite, indisputable, proven, sure, undoubted, unquestionable