—n. 1. a style of dress, including accessories and hairdos, esp. that peculiar to a nation, region, group, or historical period.
2. dress or garb characteristic of another period, place, person, etc., as worn on the stage or at balls.
3. fashion of dress appropriate to a particular occasion or season: dancing costume; winter costume. 4. a set of garments, esp. women's garments, selected for wear at a single time; outfit; ensemble.
—v.t. to dress; furnish with a costume; provide appropriate dress for: to costume a play.
—adj. 1. of or characterized by the wearing of costumes: a costume party. 2. meant for use with or appropriate to a specific costume: costume accessories.