A rancid, steaming, liquidy fecal secretion that occurs in the middle of the night, while you are asleep, after you eat a number of raw potatoes on a drunken bet. Said secretion smells like a combination of idaho spuds, raw sewage, and shame. Liquid au gratin is best enjoyed with friends, as you invite them to witness, and smell, your stench filled, mattress-goodness.
Did you get a whiff of Berko's "liquid au gratin"? The smell is nearly as disgusting as what it did to his sheets!
A euphanism for having sex. Generally used to describe a more "workman's approach" to the act. Best used to describe having sex with someone with which you have absolutely no emotional attachment. Can also be used in the in the past or current tense, for example:
I really want to "make bang" with that hot, red-headed sorority chick!