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1.
Your namesis is someone with the same name as you.
Dude A: "It's crazy - I went to meet our ad agency today and there's a guy there with the same name as me. He's got a stuffed cat on his desk and he's clearly much more interesting than me".

Dude B: "That's your namesis man, you're in deep trouble."
by Skipperton March 01, 2011