Hum Chum

A person who hums a tune/song while inside a public bathroom stall for the single purpose of trying to anger all the other people in the bathroom. They are known to hum either a rock song due to the loud volume of the song and the fast tempo, and songs popular on the internet.

There was a Hum Chum at the gym humming the Kirby theme, I think he was beat up by 5 people when he got out.