1. When you're riding your bike down a hill at such speeds that when you peddle it seems as though your chain has fallen off.

Something that is extremely cool; a cool travel destination.

For a situation to get out of control or out of hand and chaotic, like a wild night out.

I worked at a summer camp a few years ago and an inner city kid told me that this expression derives from the term off the hook. However is something is off the chain it is far more exciting and possibly even enchanting.

something that is really unique, amazing, unbelivable or, just down-right awesome

the new "off the hook"

heard first on MTV
won't last long.

See off the hook