unconceivable

too extraordinary or improbable to believe it's unconceivable that a once-promising actor could end up this way Synonyms fantastic (also fantastical), implausible, inconceivable, incredulous, unbelievable, uncompelling, incredible, unconvincing, unimaginable, unthinkableRelated Words debatable, disputable, dodgy [chiefly British], doubtable, doubtful, dubious, dubitable, far-fetched, fishy, flimsy, questionable, shaky, suspect, suspicious, unlikely, unreasonable; hopeless, impossible; absurd, comical, farcical, laughable, ludicrous, outlandish, preposterous, ridiculous, risible, silly; indefensible, insupportable, untenableNear Antonyms likely, possible, probable; reasonable; certain, incontestable, indisputable, indubitable, questionless, sure, undeniable, undoubted, unquestionableAntonyms believable, cogitable, conceivable, convincing, credible, creditable, imaginable, plausible, supposable, thinkable