bumstabbing
Quickly and painfully inserting the penis into a woman's anus forcefully, especially at an unexpected time.
"My girlfriend and I were fucking last night, and I felt like bumstabbing her. I now live on the street."
bumstabation
Masturbation involving the insertion of an object (preferably a dildo) into the anus.
I couldn't get an arse fuck, so I indulged in a little bumstabation instead