Its when the girls ass gets fucked too violently by a huge one, it turns inside out when he pulls out - so she has like an inch long protrusion of rectum hanging out. It has to be put back in by a doctor and then no anal, likely forever. Sometimes the poor girl gets it so bad it pops out everytime she craps, then they have to make her one of those in the front feces pouch bag things until it heals. Yuck!
Like I said - its not worth it! Dont take the dirt road!