Shamrock Shit Share definition Flag The resulting green poop of a delicious limited time only Shamrock Shake from McDonalds . Wow my poop was so green today; must've been a Shamrock Shit. Shamrock Shit by MichelleS February 29, 2008 0 0 Get merch Get the Shamrock Shit mug. Buy Now — $32.95 See more merch