ex cathedra
    adv 1: with the full authority of the office; "the pope must
           speak ex cathedra for an encyclical to be infallible"

Cathedra \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.
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   Ex cathedra [L., from the chair], in the exercise of one's
      office; with authority.
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            The Vatican Council declares that the Pope, is
            infallible "when he speaks ex cathedra." --Addis &
                                                  Arnold's Cath.
                                                  Dict.
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