Meaning of “costume” - Learner’s Dictionary

costume

noun uk us /ˈkɒstjuːm/
PLAY [ C, U ]

B2 a set of clothes that someone wears to make them look like someone or something else, for example in a play:

actors in costume
He arrived at the party dressed in a gorilla costume.
TYPICAL CLOTHES [ U ]

B2 a set of clothes that are typical of a particular country or time in history:

→ See also swimming costume

(Definition of “costume” from the Cambridge Learner’s Dictionary © Cambridge University Press)