Synonyms: infallible
Definition: incapable of failure or error
Usage: an infallible antidote; an infallible memory; the Catholic Church considers the Pope infallible; no doctor is infallible
Similar words: unfailing, foolproof
Definition: not liable to failure
Usage: a foolproof identification system; the unfailing sign of an amateur; an unfailing test
Similar words: unerring, inerrable, inerrant
Definition: not liable to error
Usage: the Church was...theoretically inerrant and omnicompetent-G.G.Coulton; lack an inerrant literary sense; an unerring marksman