As a musical direction: in a stately or ceremonious manner.
1An affected or self-important person.
A movement, musical passage, etc., to be played in a stately or ceremonious manner; a piece of music marked pomposo.
Of a piece, passage, etc.: played pomposo ; stately, dignified.
2Generally. Affected, pompous.
Late 18th century; earliest use found in Thomas Busby (1754–1838), composer and author. From Italian pomposo (adjective) ostentatious, ceremonious, with splendour, (of a piece of music) to be played in a stately or ceremonious manner, (noun) proud or self-important person, (adverb) in a stately or ceremonious manner from post-classical Latin pomposus.