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Person who is kind & wholesome until pushed over the line. Reference to baby JackJack from "The Incredibles" Movie.
Don't keep pushing him. He's going to go Jack-Jack.

Be careful with him. He's got a Jack-Jack personality
by moviedude March 09, 2008
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3
When one leaves his seat and calls jack jack which ultimately reserves that seat for him when he returns. Jack Jack was created long before Tap Tap and Jack Jack actually over rides all claims to tap tap. Originated in the city of Gig Harbor which was founded way before Tacoma.
When you get up, "Jack Jack".
by Chris Macky December 11, 2007
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4
a sneaky little person that works at cybercamps, and is constantly bugging owen about him being an LIT. he wears a stuipd pink ballon around his head, which has headlice.
by odubcybercamps August 04, 2009
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6
A little piece of crap (usually Asian) that is very short and likes to eat cats.
JackJack is a piece of crap.
by Jackeiwjejciis January 10, 2019
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