infallible
[adjective]
Synonyms: foolproof, certain, dependable, reliable, sure, sure-fire (informal), trustworthy, unbeatable, unfailing

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Antonyms: fallible
Contrasted words: deceivable, faulty, unsure, doubtful, dubious, questionable, uncertain, useless, worthless, unacceptable, unsatisfying, unsatisfactory
Related Words: faultless, flawless, impeccable, undeceivable, correct, exact, perfect, effective, efficacious, efficient, handy, helpful, useful, acceptable, agreeable, satisfying, satisfactory

[TahlilGaran] English Synonym Dictionary ▲

in‧fal‧li‧ble /ɪnˈfæləbəl, ɪnˈfælɪbəl/ adjective

1. always right and never making mistakes Antonym : fallible:
No expert is infallible.
an infallible memory

2. something that is infallible always works or has the intended effect ⇒ fail-safe:
He had an infallible cure for a hangover.
—infallibly adverb
—infallibility /ɪnˌfæləˈbɪləti, ɪnˌfælɪˈbɪləti/ noun [uncountable]

[TahlilGaran] Dictionary of Contemporary English ▲