Source : Webster's Revised Unabridged Dictionary (1913)

Water moccasin \Wa"ter moc"ca*sin\ (Zo["o]l.)
   A venomous North American snake ({Ancistrodon piscivorus})
   allied to the rattlesnake but destitute of a rattle. It lives
   in or about pools and ponds, and feeds largely of fishes.
   Called also {water snake}, {water adder}, {water viper}.

Source : WordNet®

water moccasin
     n 1: venomous semiaquatic snake of swamps in southern United
          States [syn: {cottonmouth}, {cottonmouth moccasin}, {Agkistrodon
          piscivorus}]
     2: any of numerous North American water snakes inhabiting fresh
        waters