Definition of ex cathedra in English:
ex cathedra
adverb & adjectiveˌɛks kəˈθiːdrəˌɛks kəˈθidrə
With the full authority of office (especially that of the Pope, implying infallibility as defined in Roman Catholic doctrine)
as adverb for an encyclical to be infallible the Pope must speak ex cathedra
as adjective this papal judgement is not ex cathedra
Synonyms
lawful, legitimate, licit, within the law, legalized, valid
Origin
Latin, 'from the (teacher's) chair', from ex 'from' and cathedra 'seat' (from Greek kathedra).
Definition of ex cathedra in US English:
ex cathedra
adverb & adjectiveˌɛks kəˈθidrəˌeks kəˈTHēdrə
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
Synonyms
lawful, legitimate, licit, within the law, legalized, valid
Origin
Latin, ‘from the (teacher's) chair’, from ex ‘from’ and cathedra ‘seat’ (from Greek kathedra).