n. (pl. -os) 1 a set or group of three. 2 Mus. a a composition for three performers. b a group of three performers. c the central, usu. contrastive, section of a minuet, scherzo, or march. 3 (in piquet) three aces, kings, queens, or jacks in one hand.
[ F & It. f. L tres three, after duo ]