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1.
To swing from some structure and let the dead weight of one's body slam into another person.

While obviously derived from hanging on the rim after a forceful dunk and letting one's body dangle in the face of an opponent for added emphasis, this act is most often done in real life while swinging from a lofted bed or ceiling fixture to knock an unsuspecting friend off balance or, if extremely successful, to the floor.
While Brad was looking the other way, Burg jumped up and grabbed the top of the doorway and went jam city on him.
by Fitterer February 02, 2006
14 0
 
2.
Basically the same as being Jammed(Under the influence of strong opiates). Just a different way to say it.
Jill: You fucked up dude?

Rob: Yah man, im right in the middle of jamcity.

"Just got back from jamcity"

"About to go kick it in jamcity"
by mothafuckinsaul October 26, 2011
0 0
 
3.
(n) A nice pair of breasts.
Her titties be so good, shit be like jam city.
by E-money E-train March 28, 2007
5 10