The Collaborative International Dictionary of English v.0.48:

Trainman \Train"man`\
   a member of the crew of a railroad train, often an assistant
   to a conductor.
   [PJC]

WordNet (r) 3.0 (2006):

trainman
    n 1: an employee of a railroad [syn: trainman, railroader,
         railroad man, railwayman, railway man]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "trainman":
   baggage man, bakehead, brakeman, brakie, butcher, conductor,
   dispatcher, fireman, footplate man, guard, lineman, porter,
   railroad man, railroader, redcap, smoke agent, stationmaster,
   stoker, switchman, trainboy, trainmaster, yardman, yardmaster