Green’s Dictionary of Slang

assfuck n.

[ass n. (2) + fuck n. (1)]
(orig. US)

1. an act of anal intercourse.

[US]G. Legman ‘Lang. of Homosexuality’ Appendix VII in Henry Sex Variants.
[US]Guild Dict. Homosexual Terms 2: ass-fuck [...] (n.): The act of pedication.
[UK]‘Linda Lovelace’ Diary 66: He gave me the best ass-fuck I’ve ever had.
[US]R.O. Scott Gay Sl. Dict. [Internet] assfuck: [...] 2. an act of anal intercourse.
[US]W.T. Vollmann Whores for Gloria 153: Ass fuck $60–$75.
www.xxx-assfuck.com [Internet] XXX ASS FUCK XXX ASS FUCK hardcore interracial anal sex pictures of xxx-rated nasty ass fucking!

2. an instance of cruel victimization.

[US]Schrader Blue Collar 14: No way was he gonna take this ass-fuck forever [HDAS].

3. an all-purpose derog. term of address.

www.imbum.com [Internet] Grunt, You ass fuck! You ripped off of me!
B. Wagner Still Holding 185: I’m an assfuck loser.

In phrases

Assfuck, Nowhere (n.)

(US) any place condered beyond civilization.

‘Chelsea G. Summers’ in Vice 28 Apr. [Internet] Our shared cluelessness, crazed hormones, and upbringing in the Middle-of-Assfuck-Nowhere, Vermont, added up to bupkis, knowledge-wise.