1. a hard outer covering of an animal, as the hard case of a mollusk, or either half of the case of a bivalve mollusk.
  2. any of various objects resembling such a covering, as in shape or in being more or less concave or hollow.
  3. the material constituting any of various coverings of this kind.
  4. the hard exterior of an egg.
  5. the usually hard, outer covering of a seed, fruit, or the like, as the hard outside portion of a nut, the pod of peas, etc.
  6. a hard, protecting or enclosing case or cover.
  7. an attitude or manner of reserve that usually conceals one’s emotions, thoughts, etc.: One could not penetrate his shell.
  8. a hollow projectile for a cannon, mortar, etc., filled with an explosive charge designed to explode during flight, upon impact, or after penetration.
  9. a metallic cartridge used in small arms and small artillery pieces.
  10. a metal or paper cartridge, as for use in a shotgun.
  11. a cartridgelike pyrotechnic device that explodes in the air.
  12. shells, Italian Cookery. small pieces of pasta having the shape of a shell.
  13. the lower pastry crust of a pie, tart, or the like, baked before the filling is added.
  14. Computers. a program providing a menu-driven or graphical user interface designed to simplify use of the operating system, as in loading application programs.
  15. Physics.
    1. any of up to seven energy levels on which an electron may exist within an atom, the energies of the electrons on the same level being equal and on different levels being unequal.
    2. a group of nucleons of approximately the same energy.
  16. a light, long, narrow racing boat, for rowing by one or more persons.
  17. the outer part of a finished garment that has a lining, especially a detachable lining.
  18. a woman’s sleeveless blouse or sweater, especially one meant for wear under a suit jacket.
  19. Nautical. the plating, planking, or the like, covering the ribs and forming the exterior hull of a vessel.
  20. tortoiseshell(def 1).
  21. a mollusk.
  22. Engineering. the curved solid forming a dome or vault.
  23. an arena or stadium covered by a domed or arched roof.
  24. a saucer-shaped arena or stadium.
  25. the framework, external structure, or walls and roof of a building: After the fire, only the shell of the school was left.
  26. a small glass for beer.
  27. the metal, pressure-resistant outer casing of a fire-tube boiler.
  28. Metallurgy.
    1. a scab on the surface of an ingot.
    2. a length of unfinished tubing.
    3. a pierced forging.
    4. a hollow object made by deep drawing.

verb (used with object)

  1. to take out of the shell, pod, etc.; remove the shell of.
  2. to separate (Indian corn, grain, etc.) from the ear, cob, or husk.
  3. to fire shells or explosive projectiles into, upon, or among; bombard.

verb (used without object)

  1. to fall or come out of the shell, husk, etc.
  2. to come away or fall off, as a shell or outer coat.
  3. to gather sea shells: We spent the whole morning shelling while the tide was out.

Verb Phrases

  1. shell out, Informal. to hand over (money); contribute; pay.


  1. resembling the empty shell of a mollusc


  1. slang an ear (esp in the phrase a word in your shell-like)


  1. the protective calcareous or membranous outer layer of an egg, esp a bird’s egg
  2. the hard outer covering of many molluscs that is secreted by the mantle
  3. any other hard outer layer, such as the exoskeleton of many arthropods
  4. the hard outer layer of some fruits, esp of nuts
  5. any hard outer case
  6. a hollow artillery projectile filled with explosive primed to explode either during flight, on impact, or after penetrationCompare ball 1 (def. 7a)
  7. a small-arms cartridge comprising a hollow casing inside which is the primer, charge, and bullet
  8. a pyrotechnic cartridge designed to explode in the air
  9. rowing a very light narrow racing boat
  10. the external structure of a building, esp one that is unfinished or one that has been gutted by fire
  11. the basic structural case of something, such as a machine, vehicle, etc
  12. physics
    1. a class of electron orbits in an atom in which the electrons have the same principal quantum number and orbital angular momentum quantum number and differences in their energy are small compared with differences in energy between shells
    2. an analogous energy state of nucleons in certain theories (shell models) of the structure of the atomic nucleus
  13. the pastry case of a pie, flan, etc
  14. a thin slab of concrete or a skeletal framework made of wood or metal that forms a shell-like roof
  15. British (in some schools) a class or form
  16. come out of one’s shell to become less shy and reserved
  17. bring out of one’s shell to help to become less shy and reserved


  1. to divest or be divested of a shell, husk, pod, etc
  2. to separate or be separated from an ear, husk, cob, etc
  3. (tr) to bombard with artillery shells

n.Old English sciell, scill, Anglian scell “seashell, eggshell,” related to Old English scealu “shell, husk,” from Proto-Germanic *skaljo “piece cut off; shell; scale” (cf. West Frisian skyl “peel, rind,” Middle Low German schelle “pod, rind, egg shell,” Gothic skalja “tile”), with the shared notion of “covering that splits off,” from PIE root *(s)kel- (1) “to cut, cleave” (cf. Old Church Slavonic skolika “shell,” Russian skala “bark, rind;” see scale (n.1)). Italian scaglia “chip” is from Germanic. Sense of “mere exterior” is from 1650s; that of “hollow framework” is from 1791. Meaning “structure for a band or orchestra” is attested from 1938. Military use (1640s) was first of hand grenades, in reference to the metal case in which the gunpowder and shot were mixed; the notion is of a “hollow object” filled with explosives. Hence shell shock, first recorded 1915. Shell game “a swindle” is from 1890, from a version of three-card monte played with a pea and walnut shells. v.1560s, “to remove (a nut, etc.) from a shell,” from shell (n.). The meaning “to bombard with shells” is first attested 1856. To shell out “disburse” (1801) is a figurative use from the image of extracting nuts. Related: Shelled; shelling.

    1. The usually hard outer covering of certain animals, such as mollusks, insects, and turtles.
    2. The hard outer covering of a bird’s egg.
    3. The hard outer covering of a seed, nut, or fruit.
    1. A set of electron orbitals that have nearly the same energy. Electrons in outer shells have greater energy than those in shells closer to the nucleus. Elements in the Periodic Table range from the lightest elements with electrons normally occupying one shell (hydrogen and helium) to the heaviest, with electrons in seven shells (radium and uranium, for instance). See more at atomic spectrum orbital subshell. See Note at metal.
    2. Any of the stable states of other particles or collections of particles (such as the nucleons in an atomic nucleus) at a given energy or small range of energies.

In addition to the idiom beginning with shell

  • shell out
  • also see:

  • in one’s shell
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