The quality or state of being infallible, or exempt from error; inerrability. Infallibility is the highest perfection of the knowing faculty. (Tillotson) papal infallibility, the dogma that the pope can not, when acting in his official character of supreme pontiff, err in defining a doctrine of Christian faith or rule of morals, to be held by the church. This was decreed by the Ecumenical Council at the Vatican, july 18.
Origin: cf. F. Infaillibilite.