Joan was happy to leave the club with John, but when they got to his place and disrobed, she decided that a night of stumpgrinding was better than going home.
Stump Grindin' occurs when a man and a woman have sex in the missionary position. The man has his legs cut off at the knee. This poses an awkward thrusting resembling that of midget porn in fast forward.
Jimmy: "Wow, did you hear about what happened last night with Tina?"
Geoffrey: "No, what?"
Jimmy: "She was stump grindin' with that amputee."
Geoffrey: "OH SHI-"