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1.
The act of two individuals bending their penis straight down and having butt sex with each other at the same time.
Joe laid down on his stomach and Dante laid down on his back. As soon as they were hard, they pointed are dicks down between our legs and began butt-piping each other.

We could have won that round of search & destroy but Joel and Christan were too busy butt-piping each other in that building.
by Palsy Chef March 21, 2011