tomboy

Etymology

First attested in Ralph Roister Doister (published 1567, written circa 1552), where it is used to describe a boisterous girl; the OED says the citation is however "generally taken" to mean a boisterous boy, and says that a use in The Old Law (published 1656, thought to have been written circa 1599) "certainly" means a boy: "must young court-tits / play tomboys' tricks with her?" By 1579 it was attested in the meaning "an immodest woman", and by no later than 1592 it had developed its modern meaning of a “girl who acts like a boy”; from tom + boy.

noun

1. A girl who behaves in a typically boyish manner. Using this term can be considered as sexist.
   His sister, his dearest and only playmate, is a tomboy at heart.
2. (Philippines, colloquial) A lesbian; butch