When a man ejaculates inside his sexual partner's anus, and then sucks out his ejaculate along with any lingering feces. He then proceeds to make out with his partner, passing the semen and feces into aforementioned partner's mouth.
John: "How was your first date with Steve?"
Morgan: "It was totally awesome. We went out for Thai, and then he introduced me to dirt balling. I've never tasted shit before."
A variation on snowballing. it is after a woman performs oral sex on her guy... but without swallowing or spitting out the spunk. She then goes to his ass ... or another individuals ass and spits the spunk in their trunk.
when Bridgetfinished sucking my C**K she took my load and dropped it in my ass that was dirt balling.