When one enters a public bathroom, due to a fear of germs, they apply an abundance toilet paper to the toilet seat that it now resembles a mummy. At this point the subject feels better about sitting on the seat.
Rachel:Yesterday was awful. I had to shit so bad while I was waiting in Penn Station. I barely made it home without having an accident.
Skeff: Yea, last time that happened to me I had no choice but to go in and mummy wrap that seat up till I felt less grossed out.
Its when you take enough toilet paper to wrap your dick after masterbating.
"I had to clean up, so I did a mummy wrap to my tool."