To empty the bladder. Synonymsbleed the liver, drain the lizard, drain the radiator, drain the snake, leak, make water, number one, pass water, pee, pee-pee, piddle, piss, shake the dew off the lily, see a man about a horse, spring a leak, squeeze the lemon, syphon the python, take a leak, take a piss, tinkle, water the horses, wee, wee-wee, whiz, wring out a kidney, wring your sock out