semi hydroplane Share definition Flag When you have a semi-boner and you piss while closing your foreskin so it fills up. Shit dawg i had to piss so badly after i fucked that slut yesterday i had to do a semi hydroplane to the toilet. semi hydroplane by Nathmathics November 25, 2016 0 0 Get merch Get the semi hydroplane mug. Buy Now — $32.95 See more merch