One who possesses the ability to clog someone's toilet to the point of OVERFLOW (not merely backup or slow flush) causing shitty water to cover the entire tile floor and parts of the adjacent hallway carpeting. This is not intentional, and happens despite multiple courtesy flushes throughout the act leading to the final shitmastering flush.
Dave: (Running out of the bathroom) Where's your mop bro?
Me: What? Why?
Dave: Your toilet's overflowing man. Shit is literally EVERYWHERE!
Me: You're the fucking shitmaster dude... mad props. Now go clean it up.