The term 'PARTY THAT'S OFF THE HOOK' can be summarized as a rager, which is a five-letter word. A rager is an informal term for a wild and exciting party. It is usually used to describe a party that is particularly fun and lively, with lots of people and music. The phrase 'off the hook' is often used to describe something that is especially good or exciting. Therefore, a party that's off the hook is one that is particularly wild and exciting.