Green’s Dictionary of Slang

1. a man who shocks the heterosexual world by openly adopting women’s clothes, thus destroying the assumptions about male/female separatism; similarly a woman doing the opposite.

1979		Maledicta III:2 236: Drag queens (seemingly fewer but louder now) are joined by men in dresses and beards; they are like The Cockettes, a gender fuck, startling (‘The only part of most straights I blow is their mind,’ says one).
2003		‘Valued Member’ posting 27 Feb. at ButchDykeBoy.com 🌐 Live with a big dyke and a genderfuck who enjoy both quiet time and partying.

2. an act of destroying such assumptions.

1976		D. Holland ‘The Politics of Dress’ in Gay Community News IV No. 10 4 Sept. in Jay & Young (1979) 401: Their role is more clearly ‘gender-fuck’.
2000		‘Ruby Tuesday’ Mon Web En Rose 🌐 Genderfuck Sending out really mixed up signals (not giving a fuck), for example wearing a miniskirt with a beard. The first time I met someone doing a genderfuck I was really impressed.