Definition: An anorak, literally a kind of parka, is used in British slang to describe a nerd or a geek. Generally, an anorak is someone obsessively interested in a very narrow subject or hobby that bores the pants off the rest of us.
Think of train spotting, plane spotting, obsessive stamp collecting, memorizing football or baseball statistics, and you've got the kind of activities an "anorak" might indulge in.
It's a mildly derisory term but often used humorously.
Anoraks are almost always men...in need of wardrobe overhauls.
Also Known As: nerd, geek, bore
Examples:
A bunch of anoraks sat at the end of the station platform for hours, making the engine numbers in their little black books.