Wordnet 3.0
NOUN (1)
1.
belief of the Roman Catholic Church that God protects the pope from error when he speaks about faith or morality;
The Collaborative International Dictionary of English v.0.48:
Infallibility \In*fal`li*bil"i*ty\, n. [Cf. F.
infaillibilit['e].]
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]
WordNet (r) 3.0 (2006):
papal infallibility
n 1: belief of the Roman Catholic Church that God protects the
pope from error when he speaks about faith or morality