The Collaborative International Dictionary of English v.0.48:

Plowman \Plow"man\, Ploughman \Plough"man\, n.; pl. -men.
   1. One who plows, or who holds and guides a plow; hence, a
      husbandman. --Chaucer. Macaulay.
      [1913 Webster]

   2. A rustic; a countryman; a field laborer.
      [1913 Webster]

   Plowman's spikenard (Bot.), a European composite weed
      (Conyza squarrosa), having fragrant roots. --Dr. Prior.
      [1913 Webster] Plowpoint

WordNet (r) 3.0 (2006):

plowman
    n 1: a man who plows [syn: plowman, ploughman, plower]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "plowman":
   Bauer, agriculturalist, agriculturist, agrologist, agronomist,
   coffee-planter, collective farm worker, crofter, cropper,
   cultivator, dirt farmer, dry farmer, farm laborer, farmer,
   farmhand, gentleman farmer, granger, grower, harvester, harvestman,
   haymaker, husbandman, kibbutznik, kolkhoznik, kulak, muzhik,
   peasant, peasant holder, picker, planter, plowboy, raiser, rancher,
   ranchman, reaper, rustic, sharecropper, sower, tea-planter,
   tenant farmer, tiller, tree farmer, truck farmer, yeoman