When you shit across the bottom of someone's windshield, so that when they turn on their windshield wipers, a glorious rainbow of shit is painted behind the wipers.
1. The act of puking, pissing, shitting, and cumming all over a person as an act of humiliation, thus creating a disgusting rainbow of different colored substances.
2. When one has so poor of a fashion sense that you can only describe what they're wearing as a "dirty rainbow."
1. I heard Alec gave your mom a dirty rainbow last night when she was passed out.
2. Did you see what Alec wore to the dance last night? He looked like a dirty rainbow!
the act of standing from an elevated position, and proceeding to surprise someone by sharting aggressively onto them, covering them in a watery brown slurry and ruining their day.