Open English Wordnet
Nouns
(n)costumethe attire worn in a play or at a fancy dress ball“he won the prize for best costume” (n)costumeunusual or period attire not characteristic of or appropriate to the time and place“in spite of the heat he insisted on his woolen costume” (n)costumethe prevalent fashion of dress (including accessories and hair style as well as garments) (n)costumethe attire characteristic of a country or a time or a social class“he wore his national costume” Verbs
(v)costume, dress updress in a costume“We dressed up for Halloween as pumpkins” (v)costumefurnish with costumes; as for a film or play