Source : Webster's Revised Unabridged Dictionary (1913)

Tuatara \Tu`a*ta"ra\, n. [Maori tuat[`a]ra; tua on the farther
   side (the back) + tara spine.]
   A large iguanalike reptile ({Sphenodon punctatum}) formerly
   common in New Zealand, but now confined to certain islets
   near the coast. It reaches a length of two and a half feet,
   is dark olive-green with small white or yellowish specks on
   the sides, and has yellow spines along the back, except on
   the neck.

Source : WordNet®

Sphenodon punctatum
     n : only extant member of the order Rhynchocephalia of large
         spiny lizard-like diapsid reptiles of coastal islands off
         New Zealand [syn: {tuatara}]