Slang for "not true".
Commonly used as a defensive response or an exclamation of denial
Person A: "You're an egg, ow"
Person B: "Not even ow!, You're an egg"
Person A: "Whatever dick! Not even! You're an egg!"
... and so on and so on.
Exclamation of denial
Person A: "Hey bro, you reckon Jane likes me?"
Person B: "Not even, bro! She thinks you're an egg!"