2) Good, bad, or extremely out of the ordinary.
Note: Both definitions an be used in both positive and pejorative sense.
I'm so happy I got promoted. My new salary is on crack.
My cell phone is on crack. I need a new one.
Used to describe something stupid, messed up or to express frustration with something
That biology report is on crack man.
Dude, Ms. Stanton's on crack! She gave me a friggen C+!!!