Many will tell you it is a combination of crazy and drunk, combining to form "crunk". That is false.
It is more or less a derivative of crank that was bastardized by youth.
The best way to relate it is to compare it to a wind up toy. You crank it repeatedly, if you crank it too much you passed the point of "crank" and have moved on to "crunk". It is a level that was not intended by design and the potential energy contained now is off the charts. When unleashed there is an unstoppable wave that is almost beyond comprehension or measurement.
If you are "crunk" you are basically a juggernaut of energy and nothing will stop you and you won't care what happens until such point that you decide to stop.
-To get crunk.
People think it means "crazy and drunk".. this is not true. Lil' Jon's style of music is called "crunk music". It is called this because it is loud, uptempo rap music. It makes you want to move and get buck and get hype. It pumps you up. It gets you crunk.