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