To "sludgeball", is to suck out the cum that is ejaculated into someone's anus, then spat into someone's mouth. Similar to snowballing, but involves the added step of man-juicing the stinkhole. Popular with gays, and swingers. "Sludgeballing" is the act of the sludge ball suck and spit, whereas the "sludge ball" is the sticky cum/shit cocktail itself.
Mike to Steve: Did you see my wife Trudy sludgeball your wife Jemima, after I came hard in Jemima's asshole?
Steve: Yeah but Trudy didn't sludgeball all of it. She held some back and gave Jemima a cum-spit facial with the rest of it. I was deep in Trudy's asshole at the time.
Both guys: Our wives are awesome. *laughter*