shell
     n 1: ammunition consisting of a cylindrical metal casing
          containing an explosive charge and a projectile; fired
          from a large gun
     2: the material that forms the hard outer covering of many
        animals
     3: hard outer covering or case of certain organisms such as
        arthropods and turtles [syn: {carapace}, {cuticle}]
     4: the hard usually fibrous outer layer of some fruits
        especially nuts
     5: the exterior covering of a bird's egg [syn: {eggshell}]
     6: a rigid covering that envelops an object; "the satellite is
        covered with a smooth shell of ice"
     7: a very light narrow racing boat [syn: {racing shell}]
     8: the housing or outer covering of something; "the clock has a
        walnut case" [syn: {case}, {casing}]
     9: a metal sheathing of uniform thickness (such as the shield
        attached to an artillery piece to protect the gunners)
        [syn: {plate}, {scale}]
     10: the hard largely calcareous covering of a mollusc
     v 1: use explosives on; "The enemy has been shelling us all day"
          [syn: {blast}]
     2: fall out of the pod or husk; "The corn shelled"
     3: hit the pitches of hard and regularly; "He shelled the
        pitcher for eight runs in the first inning"
     4: look for and collect shells by the seashore
     5: come out better in a competition, race, or conflict; "Agassi
        beat Becker in the tennis championship"; "We beat the
        competition"; "Harvard defeated Yale in the last football
        game" [syn: {beat}, {beat out}, {crush}, {trounce}, {vanquish}]
     6: remove from its shell or outer covering; "shell the
        legumes"; "shell mussels"
     7: remove the husks from; "husk corn" [syn: {husk}]
Source: WordNet® 2.0

shell n. [orig. {{Multics}} techspeak, widely propagated via Unix] 1.
   [techspeak] The command interpreter used to pass commands to an
   operating system; so called because it is the part of the operating
   system that interfaces with the outside world. 2. More generally, any
   interface program that mediates access to a special resource or {server}
   for convenience, efficiency, or security reasons; for this meaning, the
   usage is usually `a shell around' whatever. This sort of program is also
   called a `wrapper'. 3. A skeleton program, created by hand or by another
   program (like, say, a parser generator), which provides the necessary
   {incantation}s to set up some task and the control flow to drive it (the
   term {driver} is sometimes used synonymously). The user is meant to fill
   in whatever code is needed to get real work done. This usage is common
   in the AI and Microsoft Windows worlds, and confuses Unix hackers.

   Historical note: Apparently, the original Multics shell (sense 1) was
   so called because it was a shell (sense 3); it ran user programs not by
   starting up separate processes, but by dynamically linking the programs
   into its own code, calling them as subroutines, and then dynamically
   de-linking them on return. The VMS command interpreter still does
   something very like this.


Source: The Jargon File