BunyonBun"yon\, Bunion \Bun"ion\, n. [Cf. Prov. E. bunny a small swelling, fr. OF. bugne, It. bugna, bugnone. See Bun.] (Med.) An enlargement and inflammation of a small membranous sac (one of the burs[ae] muscos[ae]), usually occurring on the first joint of the great toe.