When you have your underpants pulled down and your ass put up to a water fountain. Commonly used in Bronks, Minnesota by Spooky Tony Tofu.
"Remember when we used to beat you up in the schoolyard and pull your underpants down."
"Yeah, well, No I don't remember that, actually"
"Yeah then we'd put you up to the water fountain and tell you it was a Bronks Bidet"