A hard, protective outer case or covering of an animal, such as a mollusk or crustacean. The hermit crab found a new shell to inhabit after outgrowing its old one.
The hard outer covering of a nut, seed, or egg. She cracked the walnut shell to get to the nut inside.
A hollow projectile for a cannon or other artillery, filled with explosive material. The soldiers took cover as the enemy fired a shell that exploded nearby.
A framework or structure that serves as a support or enclosure. The building's shell was completed, but the interior was still under construction.
A thin, usually spherical layer or surface, such as the outer layer of an atom's electron cloud. In chemistry, electrons are arranged in shells around the nucleus of an atom.
Computing: a command-line or graphical interface through which a user interacts with an operating system. Most developers keep a shell open to run build scripts and version-control commands.