The Collaborative International Dictionary of English v.0.48:

Hammock \Ham"mock\ (h[a^]m"m[o^]k), n. [A word of Indian origin:
   cf. Sp. hamaca. Columbus, in the Narrative of his first
   voyage, says: "A great many Indians in canoes came to the
   ship to-day for the purpose of bartering their cotton, and
   hamacas, or nets, in which they sleep."]
   1. A swinging couch or bed, usually made of netting or canvas
      about six feet long and three feet wide, suspended by
      clews or cords at the ends.
      [1913 Webster]

   2. A piece of land thickly wooded, and usually covered with
      bushes and vines. Used also adjectively; as, hammock land.
      [Southern U. S.] --Bartlett.
      [1913 Webster]

   Hammock nettings (Naut.), formerly, nets for stowing
      hammocks; now, more often, wooden boxes or a trough on the
      rail, used for that purpose. Hamose

WordNet (r) 3.0 (2006):

hammock
    n 1: a small natural hill [syn: knoll, mound, hillock,
         hummock, hammock]
    2: a hanging bed of canvas or rope netting (usually suspended
       between two trees); swings easily [syn: hammock, sack]