unquestionable adj. + Add to list US //ənˈkwɛstʃənəbəɫ// UK //ʌnkwˈɛstʃənəbəl// un·ques·tion·able SynonymsAntonymsEtymology Synonyms authenticveritable Antonyms questionableOrigin From un- + question + -able, compare questionable.