The Collaborative International Dictionary of English v.0.48:

Carapace \Car"a*pace\ (k[a^]r"[.a]*p[=a]s), n. [F.] (Zool.)
   The thick shell or shield which covers the back of the
   tortoise, or turtle, the crab, and other crustaceous animals.
   [1913 Webster]

WordNet (r) 3.0 (2006):

carapace
    n 1: hard outer covering or case of certain organisms such as
         arthropods and turtles [syn: carapace, shell,
         cuticle, shield]