- infallible (adj.)
- "exempt from error in judgment, knowledge, or opinion," early 15c., from Medieval Latin infallibilis, from in- "not, opposite of" (see in- (1)) + Late Latin fallibilis (see fallible). In reference to Popes, attested from 1870, hence infallibilism, the doctrine of this; infallibilist. Related: Infallibly.
