A person who ruins the fun or the enthusiasm of others.
"Come on, let's go to your cousin's party tonight and have some fun!"
"No, it won't be fun, and my cousin is NOT cute"
"Aw, don't be such a spoil sport!"
by sosso November 3, 2008
Petty, spiteful complaining after losing a sporting event.
The spoiled sports pummeled our mascot after we won the big game.
by RKeller1 April 19, 2010