http://alt-usage-english.org/ucle/ucle9.html :
"Anorak? comes from a Greenland Eskimo word for a type of jacket. An ?Anorak? is characteristically made of waterproof materials and has a hood attached. In recent years, it has been adopted for other purposes, most commonly as a noun to describe train-spotters, computer geeks, and unpopular college students. It has also appeared as an adjective, for example, ?He?s too Anorak for me?, with the same pejorative connotation. At the time of this writing, ?Anorak? has not yet found its place in English usage as a verb. But these things take time."
I just heard the adjectival use to mean "pedantic", or worse, "anal". At least, it seemed to me to be a bit stronger than "computer geeks" ( though not as scornful as a teenager's rejection).
On the Brit car care program, "A car is reborn", the car repair man, demonstrating piston rings or gaskets or some such, said. "Not to be anorak about this", and went on with his demo of cleaning and setting replacement parts on the engine.