Green’s Dictionary of Slang

buttfuck n.

[lit. and fig. uses of buttfuck v. (1)]

1. [1970s+] (also butt-bang) an act of anal intercourse.

2. [1980s+] a tedious piece of work, i.e. pain in the arse n. (3)

3. [1980s+] a disaster, a piece of victimization.

4. in attrib. use of sense 1.