Yiddish waterfall
While a woman is peeing in the toilet you attempt to pee through her legs into the toilet. Of course this is nearly impossible thus you end up peeing on her urinating vagina thus causing a waterfall. Not typically done for wierd sexual pleasure. Only in the case that you both have to go and the house only has one head.
Oh shit there's only one bathroom at this fucking party !!! I guess we'll just have to Yiddish waterfall babe.