1. To steal something back from someone who stole from you (i.e. jacked you).
2. To jump, attack, or otherwise harm in retaliation for the same thing having been done to you.
Popularized by the rap song of the same name.
Guy 1: Hey, there goes that dude who stole my Cd's
Guy 2: Did he lock his car door?
Guy 1: No, let's hit him with a jack back!
a party with high aspirations, but ends up being a boring sausagefest. Typically held by Canadians and usually ends in a fight, which is held by the whiny-bitch host.
Daniel: Hey bro did you go to that party last night?
Alex: Ya man but it ended up being a jack back.
Daniel: Dude that sucks.
Alex: Ya I thought it be good. But it ended up being a boring sausagefest and we just watched the laker game.
An episode of LOST that is Jack-centric.
"Dammit! ANOTHER jackback this week?