When someone is a bit of nerd but mostly geek. For example, a neek might have most of the geek traits (movies, video games, superheroes, band, etc.) but fit in with one or two of the nerd characteristics (enjoys math, school, etc.)
Girl #1: You know that kid that stays inside and plays Zelda all day? Such a geek.
Girl #2: Him? No way! He's a Mathlete!
Girl #1: Must be a neek then
A neek is someone who will grow up and go on to be successful, while the “cool” kids find out that their street cred and their stolen phones don't mean to anybody in the real world.
It's basically used to describe a nerd/geek.