A (traditionally) masculine man or woman, and especially a masculine lesbian. Often the "dominant" partner in a lesbian relationship, and especially of a butch/femme lesbian relationship.

Dressing masculinely does not make a woman into a lesbian, contrary to popular belief; it's usually more convenient.

Acting masculinely only means that's the gender role that the person identifies with; it has nothing to do with their sexual life. A highly masculine man could be gay for all we know and a very feminine man could be straight for all we know, and both of these cases are frequent.
Long, frilly dresses? Hair swept into a bun? Makeup? Silks and satins? Sweet, shy disposition? Definitely a femme.

Short hair? Denim? Leather jacket? Nose piercings? Motorcycles? Suits and ties? Loud and aggressive? How could that be more butch?
by Lorelili February 23, 2005
Masculine or Macho dress and behavior, REGARDLESS of sex or gender indentity.
"wow, that person dresses and acts in ways that are steroetypically considered masculine or macho, they are butch."
by mistress tuesday February 4, 2006
An overtly/stereotypically masculine or masculine-acting woman. can be used to denote an individual, or the dominant role in a lesbian relationship. Mostly people named Selena are butches
You see Selena over there?!
YEAH!

she's a total Butch!
by swagmf February 25, 2015
When I unknowingly approached a butch and said "excuse me sir," she punched me in the mouth.
by Orange County California February 3, 2015
A female who seems to have a very manly personality &&/or physique.

Me:"GOD!! I FRIGGIN SAW CONCETTA TODAY!!"
Danitza:"HAHAHA She's suchhh a butch."
by Breeface December 26, 2005
A woman that loooks very manly.
Damn, Breanne looks pretty butch today!
by Cody Sommer March 21, 2006
An adjective used to describe someone who is very masculine. Especially used in terms of women who have a very manly physique and have the face to match. Often used to describe lesbians and feminists.
"Sweet Jesus, I'd never go out with that butch chick, it'd be like sleeping with a guy!"
by Eej February 14, 2003