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1.
N. A person who loves to dance, eat, drink, and party with all their friends. This person is highly social and seems to know everyone @ the party. They Show up at a good time, usually appearing suddenly without making an entrance. Because of their popularity, they are often invited to multiple parties at once. They stealthily vacate and "party-hop" too their next location. Almost ninja like.
Wow, she's such a party ninja, She's hitting up my buddies party too!
by h22 tek November 05, 2010
 
2.
A person that parties so much, they become professional party people. They specialized in the unorthodox art of party. The functions of a party ninja include out competing all competitors in drinking, party games, and the art of seduction.

The party ninja, using covert methods of party, are so skilled that people can't figure out how they chugged so fast, drank so much, dominate in games, or how they seduce. .

The mysterious skills of the party ninja has long captured popular imagination of all party people worldwide.
Wow look at that party ninja, she's taking over the party!
by Tek13 22 December 09, 2010
 
3.
n; Someone who stealthily sneaks into a party or social gathering they weren't invited to. Party Ninjas are also known to tear up the place and abuse its resources, disappearing without a trace like a Ninja.
Dude, that Party Ninja is laying the smackdown on the keg of beer! Grab him! Wait, don't let him get a way!! Wha... where'd he go?
by Jin Saotome May 12, 2005