WordNet (r) 3.0 (2006):

mountain man
    n 1: a man who lives on the frontier [syn: frontiersman,
         backwoodsman, mountain man]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "mountain man":
   backwoodsman, briar-hopper, brush ape, bushman, clam digger,
   cracker, desert rat, forester, frontiersman, hillbilly,
   hinterlander, mountaineer, piny, redneck, ridge runner, woodlander,
   woodman, woodsman