infallible Synonyms

faultless perfect inerrant unequivocal undisputable trusty trustworthy true ten sure secure satisfying safe right returnless unerring unmistaken unflawed tried and true surefire sure-fire establishable error-free errorless foolproof confirmed fail-safe a-okay unquestionable unfailing reliable precise efficacious effective dependable definite correctible correct conclusive certain categorical assured accurate acceptable exact faithful firm positive omniscient necessary