Meaning

noun any large and important church

noun the principal Christian church building of a bishop's diocese

adjective relating to or containing or issuing from a bishop's office or throne

originEllipsis of cathedral church, from Middle English chirche cathederall, cathedrall chirch, calque of Late Latin ecclēsia cathedrālis (“church serving as the bishop's or archbishop's office”), from Latin ecclēsia + cathedrālis. Displaced Old English hēafodċiriċe (literally “main church, head church”).

Etymology from Wiktionary, CC BY-SA 3.0