Chitin

n. horny material covering the bodies of arthropods

Chitin (C8H13O5N)n (IPA: ) is a long-chain polymer of beta-glucose that forms a hard, semitransparent material found throughout the natural world. It is the main component of the cell walls of fungi, the exoskeletons of arthropods, such as crustaceans (e.g. crab, lobster and shrimp) and insects (e.g. ants, beetles and butterflies), the radula of molluscs and the beaks of cephalopods (e.g. squid, and octopuses). Chitin has also proven useful for several medical and industrial purposes.
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Chitin /chi·tin/ an insoluble, linear polysaccharide forming the principal constituent of arthropod exoskeletons and found in some plants, [more]Chitin - Community and Resources

Noun
1. a tough semitransparent horny substance; the principal component of the exoskeletons of arthropods and the cell walls of certain fungi
(hypernym) polysaccharide, polyose

n. chitin, horny material covering the bodies of arthropods