Green’s Dictionary of Slang

of a man, to have intercourse or masturbate between the breasts; also used of a woman, to perform intercourse in this way; thus tit-fucking n.

2000		Anon. 🌐 A second large tentacle burrowed in between her breasts. The two claws mashed her large titties together and the tentacle began to titty-fuck Ninika.
2000		M. Manning Get Your Cock Out 84: Mincey started stabbing away, giving the breathless girl a serious titfucking.
2002		Sandmann ‘Burning Down the House’ Planet Sex Stories 🌐 I tit fucked each one until I could sense they were about to blow their sticky wad.
2019		N. Walker Cherry 194: I titty-fucked her [...] . She said, ‘Do you mind not hitting me in the face with your cock’.