1 : an external supportive covering of an animal (such as an arthropod)

What is an exoskeleton in simple words?

An exoskeleton (from Greek έξω, éxō "outer" and σκελετός, skeletós "skeleton") is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton (endoskeleton) of, for example, a human. In usage, some of the larger kinds of exoskeletons are known as "shells".

What is an example of an exoskeleton?

All arthropods (such as insects, spiders and crustaceans) and many other invertebrate animals (such as shelled mollusks) have exoskeletons. Lobsters, for example, have tough outer shell systems which provide rigidity and shape to their bodies.