Definitions by Urban LXX

You have no idea 

A response that emphasizes the irony of the preceding statement.

Woman A: Your husband is unfaithful?
Woman B: You have no idea. (Husband has a gay lover)

Man A: Heard you a crazy weekend!
Man B: You have no idea. (Man B is a secret agent who used a party as a cover for a mission)

You have no idea by Urban LXX November 1, 2015