Idaho Enema
A sex move; typically performed by gay men on each other. The dominant male will insert a greased potato into the rectal cavity of his partner, and both men will masturbate all over the bed sheets. Traditionally, both men will sleep together in the semen-covered sheets after the action has been performed.
Two of my friends did an Idaho enema in my parent's bedroom at a party. Cleaning that out the next morning was a disaster! the whole room smelled like a casting couch.