The hole in one's penis from which piss comes. Largely in British use, particularly by cricketers (notably England Off-spinner John Embury) as documented by Simon Hughes in his award-winning book 'A Lot of Hard Yakka'

when the human body ejects the solids threw out ones anal which whom is seated on a toilet bowl that has released a force mushrooming the urinated water held inside the bowl up into your anal.