The usually hard outer covering that encases certain organisms, such as mollusks, insects, and turtles; the carapace. A similar outer covering on an egg, fruit, or nut. The material that constitutes such a covering. Something resembling or having the form of a shell, especially: An external, usually hard, protective or enclosing case or cover. A framework or exterior, as of a building. A thin layer of pastry. The external part of the ear. Nautical The hull of a ship. Nautical A light, long, narrow racing boat propelled by rowers. A small glass for beer. An artillery projectile containing an explosive charge. A metal or cardboard case containing the charge and primer for a piece of firearms ammunition, especially one also containing shot and fired from a shotgun. An attitude or a manner adopted to mask one's true feelings or to protect one from perceived or real danger. Physics Any of the set of hypothetical spherical surfaces centered on the nucleus of an atom that contain the orbitals of electrons having the same principal quantum number. Physics An analogous pattern of protons and neutrons within a nucleus. A usually sleeveless and collarless, typically knit blouse, often worn under another top. The outermost layer of a lined garment such as a coat or jacket: a parka with a waterproof shell. Computer Science A program that works with the operating system as a command processor, used to enter commands and initiate their execution. A company or corporation with few or no assets or independent operations that is acquired by another company in order to allow the acquiring company to conduct business under the acquired company's legitimate legal standing. To remove the shell of; shuck: shell oysters. To remove from a shell: shell peas. To separate the kernels of (corn) from the cob. To fire shells at; bombard. To defeat decisively.