A slang word in the pornographic and fetish industry that is a synonym to "Cleveland Steamer", by definition, it is when someone of the same gender rubs feces on the head of a man's penis, hence the name "Tar" + "Bell", "bell" being the head of the penis since it is shaped like a bell and "tar" represented by the feces (similar to being tarred and feathered). The man will then ejaculate and mix in his semen with the feces.
Greg: "Oooh Brian!!!! Stick in in my ass! Oh YES!!! I'm gonna... I'm gonna poop! *poops on Brian's dick head) That was soooo hawt Brian!"
Brian: I love the way you Tarbell! I'm gonna cum! Aggggghhhhhhhh!!!!