Cath"e*dra (?), n. [L., fr. Gr. seat. See Chair.]
The official chair or throne of a bishop, or of any person in high authority.
Ex cathedra [L., from the chair], in the exercise of one's office; with authority.
The Vatican Council declares that the Pope, is infallible "when he speaks ex cathedra."
Addis & Arnold's Cath. Dict.
© Webster 1913.