n. One who accepts or maintains the dogma of papal infallibility. [ 1913 Webster ]

n. [ Cf. F. infaillibilité. ] The quality or state of being infallible, or exempt from error; inerrability. [ 1913 Webster ]

Infallibility is the highest perfection of the knowing faculty. Tillotson. [ 1913 Webster ]

Papal infallibility (R. C. Ch.), 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, 1870. [ 1913 Webster ]