[knock it off] {v. phr.}, {slang}, {informal}
1. To stop talking about something considered not appropriate or nonsensical by the listener. — Used frequently as an imperative.
* /Come on, Joe, knock it off, you're not making any sense at all!/ 2. To cease doing something; to quit. — Heavily favored in the imperative.
* /Come on boys, knock it off, you're breaking the furniture in my room!/