Green’s Dictionary of Slang

1. (US) a habitual masturbator.

1962		(con. WWII) J.O. Killens And Then We Heard The Thunder (1964) 168: Corporal Solly, you old-fashioned fist-fucker.
1974		(con. 1940s) E. Thompson Tattoo (1977) 133: I feel plumb sorry for you poor Wichita fistfuckers, bein deprived of growin up without an ole cow, sheep er sow er somethin.

2. (usu. gay) one who practises fist-fucking n.

1974		J. Harry [bk title] The Fist Fucker’s Manual.
1975		Ribald (Sydney) 3 Apr. 7: Gay gives you the confessions of a fistfucker telling you how to get your arm up without bruising your knuckles.
1978		R. Price Ladies’ Man (1985) 224: If the keys were on the other side, he’d be the fist-fucker instead of the fist-fuckee, you dig?
1986		C. Stroud Close Pursuit (1988) 134: I was going to go over to Fourteenth Street, look-see if our fist-fucker is back in business.
1990		S. Morgan Homeboy 17: It ain’t a pretty sight when them Folsom Street fistfuckers get done with him.

3. (US) a generally unpleasant person.

1993

A. Linson A Pound of Flesh 22: If that treacherous fist fucker ever comes back to life, he’ll wish we’d had the good sense to nail him up on a frozen telephone pole.