A derogatory word for a white girl in an interracial relationship that stereotypically acts of her partners race. Or the feminine version of a Wigga or Wigger.
The word bun comes from the common appearance of wearing hair in a twisted up raggedy moussed or greased up bun. Bun Bitches are prone to speaking with a fake over exaggerated southern, Latin accent along with speaking excessive amounts of slang and other activities that she perceives to be used amongst her partners race and community. Although common, this term is not limited to black men and white women.
Living example: Ice T's wife CoCo