Acronym for "Super Ultra Mega Slap"
Used when insulting or scolding someone for what one thinks is tasteless, immoral, or just fucking retarded.
May also be followed by an actual slap.
Coined in 2004, by a kid with an itchy fro and another kid who was just trying to fit in.
Me - Hey Colton, I just went out and bought the new Nightmare Creatures game!
Colton - *SUMS*