The Collaborative International Dictionary of English v.0.48:

Plantation \Plan*ta"tion\, n. [L. plantatio: cf. F. plantation.]
   1. The act or practice of planting, or setting in the earth
      for growth. [R.]
      [1913 Webster]

   2. The place planted; land brought under cultivation; a piece
      of ground planted with trees or useful plants; esp., in
      the United States and West Indies, a large estate
      appropriated to the production of the more important
      crops, and cultivated by laborers who live on the estate;
      as, a cotton plantation; a coffee plantation.
      [1913 Webster]

   3. An original settlement in a new country; a colony.
      [1913 Webster]

            While these plantations were forming in Connecticut.
                                                  --B. Trumbull.
      [1913 Webster]

WordNet (r) 3.0 (2006):

plantation
    n 1: an estate where cash crops are grown on a large scale
         (especially in tropical areas)
    2: a newly established colony (especially in the colonization of
       North America); "the practice of sending convicted criminals
       to serve on the Plantations was common in the 17th century"
    3: garden consisting of a small cultivated wood without
       undergrowth [syn: grove, woodlet, orchard,
       plantation]