An orgasm of the feet, most often experienced on slush but there have been reports of people experiencing them in very wet mud or jello.
Man 1: "Dude I think I had a sludgie the other day on that slush outside the park"
Man 2: "No way, what was it like?"
Man 1: "Like Dr. Scholls was fucking me in a swamp of mushy goodness while 14 drunken polish midgets massaged my feet."
Man 2: "Yeah definitely a sludgie"