Although it’s more often used as a synonym for raincoat, an anorak is something slightly different in playground slang.

Someone that’s a little bit geeky, with strong interests or expertise in a niche area, might be referred to as an “anorak.” This probably originates from the “uncool” appearance of anorak coats and the people wearing them.

“Thomas is such an anorak when it comes to train trivia.”