The Collaborative International Dictionary of English v.0.48:

Snakebird \Snake"bird`\, n. [So named from its snakelike neck.]
   (Zool.)
   1. Any one of four species of aquatic birds of the genus
      Anhinga or Plotus. They are allied to the gannets and
      cormorants, but have very long, slender, flexible necks,
      and sharp bills.
      [1913 Webster]

   Note: The American species (Anhinga anhinga syn. Plotus
         anhinga) inhabits the Southern United States and
         tropical America; -- called also darter, and water
         turkey. The Asiatic species (Anhinga melanogaster)
         is native of Southern Asia and the East Indies. Two
         other species inhabit Africa and Australia
         respectively.
         [1913 Webster]

   2. (Zool.) The wryneck.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Anhinga anhinga
    n 1: blackish New World snakebird of swampy regions [syn: water
         turkey, Anhinga anhinga]