unchallengeable

not capable of being challenged or proved wrong the contention that there are certain unchallengeable rules governing proper grammar Synonyms accomplished, certain, inarguable, incontestable, incontrovertible, indisputable, indubitable, irrefragable, positive, sure, unanswerable, unarguable, irrefutable, undeniable, unquestionableRelated Words unambiguous, unequivocal; absolute, clear, conclusive, decisive, definite, hands-down; uncontested, uncontradicted, undisputed, unquestionedNear Antonyms controversial, debated, disputed; doubtful, dubious, iffy, inconclusive, indecisive, uncertain; ambiguous, equivocal; academic (also academical), hypothetical, speculative, theoretical (also theoretic)Antonyms answerable, arguable, contradictable, controvertible, debatable, disputable, doubtable, moot, negotiable, problematic (also problematical), questionable, refutable