A vagina that is comparable to Margaret Thatcher's. Not the alive and well Margaret Thatcher Snatch, the dead and rotting Margaret Thatcher snatch. Hence the term, Thatch Snatch.
Eric was about to go down on Jessica when he noticed all of the blisters and scabs covering her vulva. He puked in his mouth a little and decided not to pull a herpes fuck on her, she had a scabby snatch and he didn't want to catch whatever it was she had.