A fight between unfriendly opponents; either a fight with an unfriendlyopponent or a fight with an opponent who doesn't bare any unfriendliness whatsoever.
Brock Lesnar vs. Frank Mir in UFC 100, is one of the worst Grudge Matches in UFC history. After the fight, Brock (Overly confident that he won) screams at the camera and Franks face. He even tells Joe Rogan that he would rather drink Coolers light instead of bud-light (Because Coolers Light ain't paying him), and he'll "do" his wife one UFC 100 is over. Eventually, he apologies about his actions next morning in an interview.
Any of the now-familiar creepy ghosts in Japanese horror/thriller films. Aka ghost children, women with long black hair, crawly people on a ceiling, and crawly people coming out of television sets.
So named after the various forms of ghost as seen in The Grudge.