unconvincing

too extraordinary or improbable to believe the excuse for her tardiness was too unconvincing to be accepted Synonyms fantastic (also fantastical), implausible, inconceivable, incredulous, unbelievable, uncompelling, unconceivable, incredible, 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