| an external covering or integument, esp. when hard, as the shells of crustaceans (opposed to endoskeleton ). |
exoskeleton ex·o·skel·e·ton (ěk'sō-skěl'ĭ-tn)
n.
All hard parts, such as hair, teeth, and nails, that develop from the ectoderm or mesoderm in vertebrates.
A hard outer structure, such as the shell of an insect, that provides protection or support for an organism.