incapable of error
said of the pope: incapable of error in defining dogma
Infallible in religious contexts denotes the claim made by the Roman Catholic Church to be inspired by the Holy Spirit, such that, even if individual members are mistaken, the Church as a whole is able to define what counts as orthodox belief. As its head, the pope (bishop of Rome) therefore claims as infallible a limited number of formal statements of Catholic belief, issued with the full authority of his office — Dr Mel Thompson
not liable to fail; known to be effective
an infallible remedy for a hangover
infallibility /-ʹbiliti/ noun
infallibly adv
[medieval Latin infallibilis, from in-1 + fallibilis: see fallible]