in drag

Wearing clothes normally worn by the opposite sex, as in All of the actors in the revue were in drag. This expression originally alluded to male actors wearing women's apparel on stage, especially for comic purposes, but also refers to cross-dressing by homosexuals. [Colloquial; c. 1870]

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.