Definition of ex cathedra in US English:

ex cathedra

adverb & adjective

  • With the full authority of office (especially of the Pope's infallibility as defined in Roman Catholic doctrine)

    as adverb ‘for an encyclical to be infallible the Pope must speak ex cathedra’
    lawful, legitimate, licit, within the law, legalized, valid
    View synonyms

Origin

Latin, ‘from the (teacher's) chair’, from ex ‘from’ and cathedra ‘seat’ (from Greek kathedra).

Pronunciation

ex cathedra

/ˌɛks kəˈθidrə//ˌeks kəˈTHēdrə/