General terms:

* Exoskeleton: This is the most common and accurate term for a hard outer shell that provides support and protection for an animal.

* Shell: This is a broader term that can refer to the outer covering of various organisms, including those with exoskeletons, like turtles and mollusks.

* Carapace: This specifically refers to the dorsal (top) part of an exoskeleton, often found in crustaceans like crabs and lobsters.

More specific terms:

* Cuticle: This refers to the tough, outer layer of an exoskeleton, often made of chitin.

* Test: This term is used for the hard outer shell of echinoderms like sea urchins and starfish.

* Valve: This refers to each half of a bivalve's shell, like clams and oysters.

The best term to use will depend on the specific organism and the level of detail you want to convey.