cathedra [adjective] [before noun], [adverb] [not gradable] [formal] - with complete authority, or said by the Pope to be true and so accepted by all members of the Roman Catholic ChurchThis MP speaks ex-cathedra - particularly about Europe, which he seems to believe was invented by him.
EX
Meaning of EX in English
Cambridge English vocab. Кембриджский английский словарь. 2012