Where you deficate onto a woman with large breastes, preferably in between them. After the turd is in between the two dirty pillows you proceed to tit fuck her and it will leave the skidmark!
Cody: Dude I can't believe she broke up with you!?
Nathan: I know!! all i wanted is to do a Bizmark Skidmark, she's a fucking prude!
When fecal material protrudes from your rectum and your clothing picks up debris. The term skidmark comes from the resemblance to tire marks on the ground.