Definition of "Costume" :

noun: the attire worn in a play or at a fancy dress ball

"He won the prize for best costume."

noun: the attire characteristic of a country or a time or a social class

"He wore his national costume."

noun: unusual or period attire not characteristic of or appropriate to the time and place

"In spite of the heat he insisted on his woolen costume."

noun: the prevalent fashion of dress (including accessories and hair style as well as garments)

verb: dress in a costume

verb: furnish with costumes; as for a film or play