When you have Sex in a nasty truck stop bathroom while the girl holds her hands and legs on the walls like Spiderman to avoid touching the floor and the Shit on the bottom of the walls.
"My girlfriend and I were driving home and decided to stop at a gross truck stop for a quick fuck, But there was trucker shit on the floor and walls so she had to do a Dirty Morgan so I could hit it from the back."
when you are a ranger and go to your boyfriends house and give head while his sisters friends are over and you decide to do it in the living room until it hurts.
A term used to describe the act of taking your wife/girlfriend from behind and as she is begging for it harder and faster, you accidentally pull out too far and enter her anus rough and unexpectedly causing her to cry in excruciating pain then asking her if she is ok to continue so you can finish.