It's when you have anal sex with someone who has eaten too many Potato Chips and their shit is runny and Oily, then before you cum, you pull it out with oily feces still on it and cum in the air. The feces will shoot in the air resembling a Oil Derick.
Man that girl loved the black oiled cum squirting in the air when I did a Rusty Oil Derrick on her last night!
by RustyHalloween09 October 27, 2009