From Longman Dictionary of Contemporary Englishtrain spotterˈtrain ˌspotter noun [countable] British English 1 TTTDLOsomeone who collects the numbers of railway engines for fun2 BORINGsomeone who you think is boring and only interested in unimportant details —trainspotting noun [uncountable]
Examples from the Corpus
train spotter• Here is the story of one of them, Derek, the most unsuccessful train spotter in the world. 