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):

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