/ ˈkɒstjuːm; NAmE ˈkɑːstuːm/ noun
1.
[ C , U ] the clothes worn by people from a particular place or during a particular historical period
—see also national costume
2.
[ C , U ] the clothes worn by actors in a play or film / movie, or worn by sb to make them look like sth else :
The actors were still in costume and make-up.
She has four costume changes during the play.
He went to the party in a giant chicken costume.
a costume designer
3.
[ C ] ( BrE , informal ) = swimming costume
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WORD ORIGIN
early 18th cent.: from French , from Italian costume custom, fashion, habit, from Latin consuetudo , from consuetus , past participle of consuescere accustom, from con- (expressing intensive force) + suescere become accustomed.