An extremely wet, sexually aroused vagina that is extremely wooly, overly hairy and untrimmed. Generally has hair running form the mons through the taint and up the ass crack. May also be known as sasquatch crotch.
Roger picked up a girl at closing time at the local bar. He took her home for sex but when she got naked and exposed her Wet Sweater, he just couldn't do it and pretend to pass out.