shell / shel/ • n. 1. the hard protective outer case of a mollusk or crustacean: cowrie shells| the technique of carving shell. ∎  the thin outer covering of an animal's egg, which is hard and fragile in that of a bird but leathery in that of a reptile. ∎  the outer case of a nut kernel or seed. ∎  the carapace of a tortoise, turtle, or terrapin. ∎  the wing cases of a beetle. ∎  the integument of an insect pupa or chrysalis. ∎  (one's shell) fig. used with reference to a state of shyness or introversion: she'll soon come out of her shell with the right encouragement.2. something resembling or likened to a shell because of its shape or its function as an outer case: pasta shells baked pastry shells filled with cheese. ∎  the walls of an unfinished or gutted building or other structure: the hotel was a shell, the roof having collapsed completely. ∎ fig. an outer form without substance: he was a shell of the man he had been previously. ∎  a light racing boat used in the sport of crew. ∎  a woman's sleeveless sweater or blouse. ∎  the metal framework of a vehicle body. ∎  an inner or roughly made coffin. ∎  the handguard of a sword. ∎  Physics each of a set of orbitals around the nucleus of an atom, occupied or able to be occupied by electrons of similar energies.3. an explosive artillery projectile or bomb: the sound of the shell passing over, followed by the explosion | [as adj.] shell holes. ∎  a hollow metal or paper case used as a container for fireworks, explosives, or cartridges. ∎  a cartridge.4. Comput. short for shell program.• v. 1. [tr.] bombard with shells: the guns started shelling their positions.2. [tr.] remove the shell or pod from (a nut or seed): they were shelling peas | [as adj.] (shelled) shelled Brazil nuts. 3. [intr.] gather seashells: there was nothing to do except swim or go shelling on the beaches.PHRASAL VERBS: shell something out (or shell out) inf. pay a specified amount of money, esp. an amount that is resented as being excessive: it doesn't make sense to shell out $8.50 for an elevator ride.DERIVATIVES: shelled adj. [in comb.] : a soft-shelled clam. shell-less adj.shell-like / -ˌlīk/ adj.shell·y / ˈshelē/ adj.