noun
: conventional dress for formal or semiformal evening social occasions: as
a. : a woman's gown with skirt usually of floor or ankle length
b.
(1) : men's clothing consisting of a tailcoat and matching trousers usually in black or midnight blue, a white stiff-bosomed shirt, and white bow tie
(2) : men's clothing consisting of a tuxedo jacket usually in black, midnight blue, or white, a black bow tie, a stiff-bosomed or soft pleated shirt, and usually a cummerbund — compare morning dress