anorak

noun2

1. •
   A heavy weatherproof jacket with an attached hood; a parka or windcheater.

   • Don't ever use the hood on your anorak; and, if you do, for heaven's sake don't pull the string tight so that you peep out like a little baby in a siren suit. — 1980
2. •
   (UK, slang) A person with an unusual or obsessive interest in a niche subject, especially trains.