Source : Webster's Revised Unabridged Dictionary (1913)

Snapping \Snap"ping\,
   a. & n. from {Snap}, v.

   {Snapping beetle}. (Zo["o]l.) See {Snap beetle}, under
      {Snap}.

   {Snapping turtle}. (Zo["o]l.)
   (a) A large and voracious aquatic turtle ({Chelydra
       serpentina}) common in the fresh waters of the United
       States; -- so called from its habit of seizing its prey
       by a snap of its jaws. Called also {mud turtle}.
   (b) See {Alligator snapper}, under {Alligator}.

Source : WordNet®

snapping turtle
     n : large aggressive freshwater turtle with powerful jaws