Infallible means never making a mistake. An infallible method, nobody is infallible, an infallible memory.
It is nearly always used in the negative, since nothing is. In Catholic doctrine, papal infallibility is a narrow and much misunderstood claim: it applies only to formal definitions of doctrine and has been invoked very rarely.
1adjectiveinfallibleNever making a mistake.
“Even the best doctors are not infallible and sometimes get a diagnosis wrong.”
infallible is a quality.
in-FALL-ible → it never FALLs into a mistake
It never falls into a mistake, not once, not ever.
hooks ontofall
Medieval Latin infallibilis, in-, not, plus fallibilis, from fallere, to deceive. Fail is a relative.
Latin
in-
Medieval Latin
īnfallibilis
English, today
infallible
From Medieval Latin īnfallibilis, from Latin in- + fallibilis. Compare French infaillible. by surface analysis, in- + fallible.
Etymology from Wiktionary, CC BY-SA