A total bummer. Used most regularly by teenage, bro-type males to describe failed vodka-fueled hook ups or parties, but can also describe daily annoyances.
Bro 1: Yo, I was legit gonna tap that, but then she threw up all over herself and then she "wasn't in the mood anymore."
It's 'ol Buzz Killington, the old guy with a top hat that appears when you are having a crazy party. Basically he stops the drinking/smoking and proceeds to describe sketches of english people on bikes.
Peter: ''Man, that buzz kill was almost as bad as when Buzz Killingtonshowed upat that party.'' (Cut away)