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 2: Did he lock his car door?
Guy 1: No, let's hit him with a jack back!
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.