WordNet (r) 3.0 (2006):

infantryman
    n 1: fights on foot with small arms [syn: infantryman,
         marcher, foot soldier, footslogger]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "infantryman":
   Zouave, ambulator, backpacker, bersagliere, carabineer, chasseur,
   dogface, doughfoot, expert rifleman, foot passenger, foot soldier,
   foot traveler, footslogger, fusileer, grenadier, grunt, hiker,
   hitchhiker, hoofer, jaywalker, light infantryman, marcher,
   marksman, musketeer, paddlefoot, pedestrian, peripatetic, rifle,
   rifleman, sharpshooter, sniper, trailsman, tramper, walker,
   walkist