Heard exact changes from an authoritative source

Wiktionary Word definitions in Wiktionary
a. With authority based on one's rank or office. adv. With authority based on one's rank or office.

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
Latin, literally "from the (teacher's) chair," from ex "out of" (see ex- ) + cathedra (see cathedral ).

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
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. Ex cathedra [L., from the chair], in the exercise of one's office; with authority. The Vatican Council declares ...

Wikipedia Word definitions in Wikipedia
Ex Cathedra is a British choir and early music ensemble based in Birmingham in the West Midlands , England . It performs choral music spanning the 15th to 21st centuries, and regularly commissions new works. Ex Cathedra was founded in Birmingham in 1969 ...