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2.
An event or action incurring annoyance, inconvenience, or hassle.
You're really jammin' me up right now.

Having to have to go to downtown Seattle in rush hour was a real jam-up.

Tony was really jammed up by Schmid's use of Nova Gas in Black Ops.
by RitterKreuz April 18, 2011
 
1.
adj.
Used to denote something incredibly extraordinary, awesome or amazing. Not to be confused with jammed up, which is a bad thing.
(1)Wow, did you go to Chad's house the other night?!? That guy knows how to throw a jam up party!
(2) How about that girl named Whitney at Chad's party? Man, she has a jam up rack!
by -The Legend- July 28, 2008