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14.
A person who intentionally takes the joy of another person and brutally murders it with no remorse.
Girl: Yesh, finally Full Metal Alchemist. Oh how I've longed for you. *kisses television*
Mom: No FULL METAL ALCHEMIST. Japan is evil.
Girl: Geez Mom, you're such a kill-joy!

Girl: Yesh, No school because of snow!
Weather Man: Looks like school is back in session due to the sudden elevation of tempurature.
Girl: Geez Mr. Meteorologist Man Guy, you're such a kill-joy.
by Buttonsinfallcolours August 09, 2006
 
1.
Someone who wants to ruin someone elses fun.
The killjoy tattled to the apartment manager, after he saw Mike enter his apartment with a gorgeous woman at midnight.
by Ronald Clifford Buckman August 09, 2003
 
2.
Reference to "Danger Days: The True Lives of the Fabulous Killjoys", the (as yet to be released) album by My Chemical Romance.

Outsider fighting against social/corporate suffocation.

Non-conformist.

Rebel.
"Killjoys, make some noise!"

Search "Na Na Na trailer" on YouTube for the best definition/example.
by Elph7777 October 01, 2010
 
3.
a person who takes the fun out of things for other people
You killjoys need to loosen up. I want you to have some fun this time.
by Light Joker May 17, 2005
 
4.
One who kills fun and/ or joy and happiness.

Also see party pooper
Dude!! I was about to get laid, but then my dad walked in and freaked out. He's such a killjoy.
by Senor Anon May 06, 2008
 
5.
1)someone who doesn't want others to enjoy something because it is in his/her taste.

2) someone who doesn't like happiness, laughter or fun especially when the person is not involved/invited and comes in to ruin it.
1) James is always coming in and cutting off the game because he sucks at it, he is such a killjoy.

2) Whenever we are laughing, joking or playing a fun game, it bugs jim's father so much that he runs downstairs and ruins it for us. tsk, tsk...such a killjoy.
by COOLMASTER X October 15, 2009
 
6.
somebody who ruins fun for other people
I wont bother making a christmas turkey next year

Bloody hell! Stop being a bloody Killjoy
by mickmickman July 10, 2008
 
7.
A person who deprives everyone of their joy in the moment, sometimes resulting in silence.
When Bob walked in, and then everybody's expression changed and everyone stopped talking, Bob is a real killjoy
by Chieftawsmcool January 17, 2011