To be hack is to be bad at the thing you do best, or something you like to do. You fail at it. Being a hackshow is essentialy putting on a show of failure. Trying, and trying again to do something right, without any progress.
Bob: What is that, like, your twentieth try at trying to hit the ball with your racket?
Fred(trying desparetly to hit the ball): Yeah, but i think im going to get it soon!
Bob: GIVE IT UP YOU HACKSHOW.