hellbender

from WordNet (r) 3.0 (2006)

hellbender
    n 1: large salamander of North American rivers and streams [syn:
         {hellbender}, {mud puppy}, {Cryptobranchus alleganiensis}]

from The Collaborative International Dictionary of English v.0.48

Hellbender \Hell"bend`er\, n. (Zool.)
   A large North American aquatic salamander ({Protonopsis
   horrida} or {Menopoma Alleghaniensis}). It is very voracious
   and very tenacious of life. Also called {alligator}, and
   {water dog}.
   [1913 Webster]