1. Not fallible; not capable of erring; entirely exempt from liability to mistake; unerring; inerrable.
2. Not liable to fail, deceive, or disappoint; indubitable; sure; certain; as, infallible evidence; infallible success; an infallible remedy. To whom also he showed himself alive, after his passion, by many infallible proofs. (acts i. 3)
3. Incapable of error in defining doctrines touching faith or morals. See papal infallibility, under infallibility.
Origin: Pref. In- not – fallible: cf. F. Infallible.