The Collaborative International Dictionary of English v.0.48:

Camper \Camp"er\, n.
   1. One who lodges temporarily in a hut or camp, especially
      who sleeps in a wilderness for recreation.
      [1913 Webster]

   2. A person who stays at a summer camp or day camp.
      [PJC]

   3. A vehicle, such as a small truck, or a pickup truck with a
      hood over the back, equipped for convenience while camping
      out.
      [PJC]

   happy camper a person who is pleased with the situation in
      which s/he finds him/herself. Often used ironically or in
      understatement, especially in the negative; as, the
      passengers left behind on the island were not a bunch of
      happy campers.
      [PJC] Campestral

WordNet (r) 3.0 (2006):

camper
    n 1: someone living temporarily in a tent or lodge for
         recreation
    2: a recreational vehicle equipped for camping out while
       traveling [syn: camper, camping bus, motor home]

Moby Thesaurus II by Grady Ward, 1.0:

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