The Collaborative International Dictionary of English v.0.48:

Planter \Plant"er\, n.
   1. One who, or that which, plants or sows; as, a planterof
      corn; a machine planter.
      [1913 Webster]

   2. One who owns or cultivates a plantation; as, a sugar
      planter; a coffee planter.
      [1913 Webster]

   3. A colonist in a new or uncultivated territory; as, the
      first planters in Virginia.
      [1913 Webster]

   4. a movable box or a fixed low, open structure, as of brick,
      in which plants are grown for decorative purposes.
      [PJC]

WordNet (r) 3.0 (2006):

planter
    n 1: the owner or manager of a plantation [syn: planter,
         plantation owner]
    2: a worker who puts or sets seeds or seedlings into the ground
    3: a decorative pot for house plants

Moby Thesaurus II by Grady Ward, 1.0:

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