1cos·tume 
/ˈkɑ:ˌstu:m, Brit ˈkɒˌstju:m/ noun
plural cos·tumes /ˈkɑ:ˌstu:m, Brit ˈkɒˌstju:m/ noun [count] 1 : the clothes that are worn by someone (such as an actor) who is trying to look like a different person or thing
▪ children in their Halloween costumes ▪ a colorful clown costume 2 : the clothes worn by a group of people especially during a particular time in the past
▪ a formal 18th-century Japanese costume ▪ The dancers were dressed in their national costumes. [=the clothing that is traditional in their countries] 3 Brit : swimsuit
▪ children in their Halloween costumes ▪ a colorful clown costume
▪ a formal 18th-century Japanese costume ▪ The dancers were dressed in their national costumes. [=the clothing that is traditional in their countries]
in costume
: wearing a costume
▪ If all the actors are in costume, we're ready to begin. ▪ The waiters were all in ancient Roman costume.
▪ If all the actors are in costume, we're ready to begin. ▪ The waiters were all in ancient Roman costume.
— cos·tumed /ˈkɑ:ˌstu:md, Brit ˈkɒˌstju:md/ adjective
▪ costumed actors
/ˈkɑ:ˌstu:md, Brit ˈkɒˌstju:md/ adjective ▪ costumed actors
