WordNet (r) 3.0 (2006):

rancher
    n 1: a person who owns or operates a ranch

Moby Thesaurus II by Grady Ward, 1.0:

69 Moby Thesaurus words for "rancher":
   Bauer, agriculturalist, agriculturist, agrologist, agronomist,
   breaker, breeder, broncobuster, buckaroo, cattleman,
   coffee-planter, collective farm worker, cow keeper, cowman,
   crofter, cropper, cultivator, dairy farmer, dairyman, dirt farmer,
   dry farmer, equerry, farm laborer, farmer, farmhand, farrier,
   gentleman farmer, granger, grazier, groom, grower, harvester,
   harvestman, haymaker, horseshoer, hostler, husbandman, kibbutznik,
   kolkhoznik, kulak, muzhik, peasant, peasant holder, picker,
   planter, plowboy, plowman, raiser, ranchero, ranchman, reaper,
   rustic, sharecropper, sheepman, sower, stableboy, stableman,
   stock raiser, stockbreeder, stockkeeper, stockman, tamer,
   tea-planter, tenant farmer, tiller, trainer, tree farmer,
   truck farmer, yeoman