Source : Webster's Revised Unabridged Dictionary (1913)

Gila monster \Gi"la mon"ster\ (Zo["o]l.)
   A large tuberculated lizard ({Heloderma suspectum}) native of
   the dry plains of Arizona, New Mexico, etc. It is the only
   lizard known to have venomous teeth.

Source : WordNet®

Gila monster
     n : large orange and black lizard of southwestern United States;
         not dangerous unless molested [syn: {Heloderma suspectum}]