Green’s Dictionary of Slang

an act of fellatio, usu. in gay use.

1905		Memoir of a Voluptuary (1996) 90: ‘I should suggest a “face-fuck”,’ Blackie answered [...] ‘I will show you what I mean’ [Simes:DLSS].
a.1972		‘Jack Stryker’ Ride a Cocked Thumb 107: ‘[A] guy can’t go through a face fuck like that and not cream a little himself’ [Simes:DLSS].
1985		‘J. Dagion’ (ed.) Trash 22: He shoved it all the way down my throat and started a slow deep face-fuck.
1999		Straight Man Tales (N.J.) Aug. 26/2: ‘Fuck his mouth hard so we can see what that’s like. I want to see what a hard facefuck looks like’ [Simes:DLSS].