The Collaborative International Dictionary of English v.0.48:

Mountaineer \Moun`tain*eer"\ (moun`t[i^]n*[=e]r"), n. [OF.
   montanier, LL. montanarius. See Mountain.]
   1. An inhabitant of a mountain; one who lives among
      mountains.
      [1913 Webster]

   2. A rude, fierce person. [Obs.]
      [1913 Webster]

            No savage fierce, bandit, or mountaineer. --Milton.
      [1913 Webster]

   3. A person who climbs mountains for sport.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

mountaineer \moun`tain*eer"\, v. i.
   To live or act as a mountaineer; to climb mountains.
   [1913 Webster]

         You can't go mountaineering in a flat country. --H.
                                                  James.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mountaineer
    n 1: someone who climbs mountains [syn: mountaineer, mountain
         climber]
    v 1: climb mountains for pleasure as a sport

Moby Thesaurus II by Grady Ward, 1.0:

73 Moby Thesaurus words for "mountaineer":
   adventurer, alpinist, ascender, astronaut, backwoodsman,
   briar-hopper, brush ape, bumpkin, bushman, camper, clam digger,
   climber, clodhopper, comers and goers, commuter, cosmopolite,
   cracker, cragsman, cruiser, desert rat, excursionist, explorer,
   fare, forester, frontiersman, globe-girdler, globe-trotter, goer,
   hajji, hayseed, hick, hillbilly, hinterlander, jet set, jet-setter,
   journeyer, mariner, mountain man, palmer, passenger, passerby,
   pathfinder, pilgrim, piny, pioneer, provincial, redneck,
   ridge runner, rubberneck, rubbernecker, sailor, sightseer,
   straphanger, tourer, tourist, trailblazer, trailbreaker, transient,
   traveler, trekker, tripper, upclimber, viator, visiting fireman,
   voortrekker, voyager, voyageur, wayfarer, woodlander, woodman,
   woodsman, world-traveler, yokel