The protective or defensive outer layer or covering of an animal or (occasionally) a plant. Formerly also (in abstract sense): †natural protection…

The hard external covering of an animal or plant; a shell, test, husk, etc.; spec. the hard chitinous integument or ‘shell’ of Crustaceans.

In an animal or plant: (provision with) hard, sharp, or tough structures or appendages offering physical protection or a means of attack…

The protective shell or scales of certain animals.

The integument of an armadillo, glyptodon, ostraciont, etc.; the elytron of an insect; the cast skin of a pupa.

In various technical senses. Anatomy, Zoology, etc. Variously applied to the hard protective covering of parts of the body of different animals, as…