The sport of taking off the porcelain lid of the toilet tank and pooping in the tank of the toilet, thus causing the toilet's owner many days of dirty flushing and unexplained stench.
Top-shelfing
Example 1:
"Dude, I heard you got fired last week...sorry to hear that."
"That's OK man, I top-shelfed them before I left."
Example 2:
"Damn, Jimmy your apartment stinks!"
"Did Sarah top-shelf you when you broke up with her?"
You go into a toilet stall, close the door, put the seat and the lid down, and poop on the lid. This is called top shelfing it. Then you go to another stall and take care of the clean up work. Wash your hands, and sneak out of the bathroom unnoticed. Works best in the middle of the night.