WordNet (r) 3.0 (2006):

hiker
    n 1: a foot traveler; someone who goes on an extended walk (for
         pleasure) [syn: hiker, tramp, tramper]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "hiker":
   ambulator, backpacker, foot passenger, foot soldier, foot traveler,
   footslogger, hitchhiker, hoofer, infantryman, jaywalker, marcher,
   paddlefoot, pedestrian, peripatetic, trailsman, tramper, walker,
   walkist