Definition of "trainspotter"

trainspotter

noun
plural trainspotters
1. A person whose hobby is train spotting.
  Quotations
  `So are you like one of those anorak wearing trainspotter types?'
  2005, Sean Dooley, The Big Twitch, Sydney: Allen and Unwin, page 2
  Above all, I remember the noise and smell of the steam locomotives, and it was those journeys that turned me into a trainspotter, which meant that soon a pencil, notebook and the Ian Allan locospotter's guide became essential items for the trip.
  2021 July 28, Christian Wolmar, “Forgotten by the railways, but ripe for the exploring”, in RAIL, number 936, page 34
2. (by extension) An obsessive follower of any minority interest or hobby.