The act of having Unprotected sex with a bowl of mashed potatoes and then using semen to cover them with a "buttery" coating. Served to a friend and or enemy.
"Dude, did you mashpotaturbate in my mashed potatoes?"
"Of course not man!"
"Then why is there a pube in it?!"
"Of course not man!"
"Then why is there a pube in it?!"
by Jmulz May 18, 2010
Get the Mashpotaturbatemug.