When a girl sits backwards atop a naked man, who subsequently pushes his erect penis into her anus. At this point, said girl bounces up and down. It is a form of anal sex, so is used primarily for the pleasure of the man.
Sarah wanted to try anal sex for the first time, and allowed Jeff to pick the type. He chose the Monkey Union. On the bed, Sarah stood up, turned around squatted, and closed her eyes as his penis entered her anus.
by ILOVEMONKEYUNION March 11, 2009