Doing something, usually with no specific plan, and with no real ending or meaning, other than thoroughly enjoying what you did.
It should also be something you can recall in your mind as having had a "Great Time".
"That is off the hook for real" would be the literal meaning of the phrase. It means that something is extremely novel and interesting, and that you're dumb enough to think you sound cool adding "izzle" to the end of your words.
Dude A: Hey dude, have you seen Frank's new car?
Dude B: Why yes I have. That tizzle off the hizzlefoshizzle.
Dude A: WTF?!?!?!