Source : Webster's Revised Unabridged Dictionary (1913)

Hamadryad \Ham"a*dry`ad\, n.; pl. E. {Hamadryads}, L.
   {Hamadryades}. [L. Hamadryas, -adis, Gr. ?; ? together + ?
   oak, tree: cf. F. hamadryade. See {Same}, and {Tree}.]
   1. (Class. Myth.) A tree nymph whose life ended with that of
      the particular tree, usually an oak, which had been her
      abode.

   2. (Zo["o]l.) A large venomous East Indian snake
      ({Orhiophagus bungarus}), allied to the cobras.

Source : WordNet®

hamadryad
     n 1: the nymph or spirit of a particular tree
     2: large cobra of southeastern Asia and the East Indies; the
        largest venomous snake; sometimes placed in genus Naja
        [syn: {king cobra}, {Ophiophagus hannan}, {Naja hannah}]