Source : Webster's Revised Unabridged Dictionary (1913)

Hellbender \Hell"bend`er\, n. (Zo["o]l.)
   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}.

Source : WordNet®

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