What is Trap Door?
1.
A pair of pants or shorts with a zipper or hole in the back. Making insertion of genitalia easier.
Did you guys see her pants today? It looks like there is a Trap door there.
See
2.
when getting your partner from behind, you secretly get a sharp object of some sort and make a decent sized wound on the upper thigh and then proceed to finger the wound.
helen: what are those wounds all over your thighs?
gladys: oh, those are trap doors
