gender bender

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One whose dress or behavior does not conform to conventional gender roles.
• noun Something, such as a theatrical performance or a book, whose portrayal of gender roles is nontraditional or androgynous.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun idiomatic, colloquial a person who dresses in the clothes of another sex; a transvestite