a theatrical role that is regularly or frequently played by an actress in male costume
About the Word:
Men, not women, traditionally wear breeches (a type of short pants), but women, not men, fill the breeches part.
In Shakespeare's day, male actors played the roles of women; by the mid17th century, after the Puritan ban on theater had ended, women were playing female parts. The notion of the breeches part reintroduced novelty as women donned pants to play traditionally male roles. A modernday breeches part is the role of Peter Pan.