WordNet (r) 3.0 (2006):

straphanger
    n 1: a commuter who uses public transportation
    2: a standing subway or bus passenger who grips a hanging strap
       for support

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "straphanger":
   adventurer, alpinist, astronaut, camper, climber, comers and goers,
   commuter, cosmopolite, cruiser, excursionist, explorer, fare,
   globe-girdler, globe-trotter, goer, hajji, jet set, jet-setter,
   journeyer, mariner, mountaineer, palmer, passenger, passerby,
   pathfinder, pilgrim, pioneer, rubberneck, rubbernecker, sailor,
   sightseer, tourer, tourist, trailblazer, trailbreaker, transient,
   traveler, trekker, tripper, viator, visiting fireman, voortrekker,
   voyager, voyageur, wayfarer, world-traveler