1US informal Female; feminine.
2 informal, derogatory Of a man, his appearance, etc.: resembling, characteristic of, or suggestive of a woman; effeminate.
Sometimes with implication of homosexuality.
3 informal Designating a lesbian whose appearance, behaviour, identity, etc., is seen as traditionally feminine; that resembles or is suggestive of a femme.
1950s; earliest use found in Billboard. From fem- + -y; perhaps influenced also by femme or its etymon French femme.