Bungthump

Due to the misinterpretation of a bung as a "butthole," a bungthump is slang for when two or more people, whether of the same gender or not, that are more than acquaintances lay on the ground in a circle on knees and elbows, each facing one another's rears in counter-clockwise direction, and thump the anus of the person in front of them with the middle finger on their right hand. This is commonly practiced at frat parties and backstage for good luck at metal concerts.

Hey man, I hear we missed out on an awesome bungthump at the wedding party Friday.