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 10, 2008
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When a guy is jacking off and is interrupted by a second individual who "lends a hand" and finishes the job.Ideally,the interloper could be the wife,girlfriend,a hot maid,or cute neighbor girl. Strangely,the good samaritan could be a sister,grandma,brother or roommate.
I was choking the chicken when my sister's hot friend barged in the bathroom and jack jacked me.
by wolfbait51 May 2, 2011
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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 12, 2007
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a dude who is always lifting big things.

when alcohol becomes involved don't go near bro, he will fight u

loves a romp
claims an amateur mui tai fighter would beat Mike Tyson
damn bro is at the gym, he is a total jack jack !!
by kinglegend69 August 23, 2022
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A Product made from mixing a bowl of "Apple Jacks" with a can of "coke." This is said to have great effects on your body and increase your testosterone level and get you JACKED.
"Man I love my Jacked-Jacks"

Before using Jacked-Jacks: "I can't lift this church!"

After using Jacked-Jacks: " I CAN LIFT THIS CHURCH!!"

by Anthony Monty May 8, 2007
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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 4, 2009
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