A phrase used to mock someone that is not cool or doesn't have "cool points". (Cool points are entirely made up and based on a number scale dealing with how much someone likes you.)
John: Hey, did you see those girls?
Sean: Wow, they're pretty gay.
John: I know. Negative infinity cool points!
John: Ellie, shut up. Negative cool points for you!
Ellie: ....you have no life....