1. Disregard that; don't worry or bother yourself about it. A: "What did you say?" B: "Never mind, it wasn't important."
2. Especially not, considering what was just said. He can barely write a coherent email, never mind an entire book!
Forget it!; It's not important! Sally. What did you say? Jane: Never mind! It wasn't important. John: I tried to get the book you wanted, but they didn't have it. Shall I try another store? Mary: No, never mind.
See also: never