1. [n]  a bar of magnetic material (as soft iron) that passes through a coil and serves to increase the inductance of the coil
2. [n]  the chamber of a nuclear reactor containing the fissile material where the reaction takes place
3. [n]  the choicest or most essential or most vital part of some idea or experience; "the gist of the prosecutor's argument"; "the heart and soul of the Republican Party"; "the nub of the story"
4. [n]  the central meaning or theme of a speech or literary work
5. [n]  a small group of indispensable persons or things; "five periodicals make up the core of their publishing program"
6. [n]  an organization founded by James Leonard Farmer in 1942 to work for racial equality
7. [n]  the center of an object; "do not eat the apple core"
8. [n]  the central part of the earth
9. [n]  a cylindrical sample of soil or rock obtained with a hollow drill
10. [v]  remove the core or center from; "core an apple"

1. \Core\ (k[=o]r), n. [F. corps. See {Corps}.]
   A body of individuals; an assemblage. [Obs.]
         He was in a core of people.              --Bacon.
   

2. \Core\, n. [Cf. {Chore}.] (Mining.)
   A miner's underground working time or shift. --Raymond.
   Note: The twenty-four hours are divided into three or four
         cores.
   

3. \Core\, n. [Heb. k[=o]r: cf. Gr. ko`ros.]
   A Hebrew dry measure; a cor or homer. --Num. xi. 32 (Douay
   version).
   

4. \Core\, n. [OF. cor, coer, cuer, F. c[oe]ur, fr. L. cor
   heart. See {Heart}.]
   1. The heart or inner part of a thing, as of a column, wall,
      rope, of a boil, etc.; especially, the central part of
      fruit, containing the kernels or seeds; as, the core of an
      apple or quince.
            A fever at the core, Fatal to him who bears, to all
            who ever bore.                        --Byron.
   2. The center or inner part, as of an open space; as, the
      core of a square. [Obs.] --Sir W. Raleigh.
   3. The most important part of a thing; the essence; as, the
      core of a subject.
   4. (Founding) The prtion of a mold which shapes the interior
      of a cylinder, tube, or other hollow casting, or which
      makes a hole in or through a casting; a part of the mold,
      made separate from and inserted in it, for shaping some
      part of the casting, the form of which is not determined
      by that of the pattern.
   5. A disorder of sheep occasioned by worms in the liver.
      [Prov. Eng.] --Halliwell.
   6. (Anat.) The bony process which forms the central axis of
      the horns in many animals.
   {Core box} (Founding), a box or mold, usually divisible, in
      which cores are molded.
   {Core print} (Founding), a projecting piece on a pattern
      which forms, in the mold, an impression for holding in
      place or steadying a core.
   

5. \Core\, v. t. [imp. & p. p. {Cord} (k?rd); p. pr. & vb. n.
   {Coring}.]
   1. To take out the core or inward parts of; as, to core an
      apple.
            He's likee a corn upon my great toe . . . he must be
            cored out.                            --Marston.
   2. To form by means of a core, as a hole in a casting.
   

6. \Core\, n. (Elec.)
   A mass of iron, usually made of thin plates, upon which the
   conductor of an armature or of a transformer is wound.
   

1. Main memory or RAM. This term dates from the days of ferrite core memory; now archaic most places outside IBM, but also still used in the Unix community and by old-time hackers or those who would sound like them.

Some derived idioms are quite current; "in core", for example, means "in memory" (paged in, as opposed to "on disk", paged out), and both core dump and the "core image" or "core file" produced by one are terms in favour. Some varieties of Commonwealth hackish prefer store.

[Jargon File]

2. An integrated circuit design, usually for a microprocessor, which includes only the CPU and which is intended to form part of a complete circuit design which incorporates other circuits on the same chip such as cache, memory management unit, I/O ports and timers.

The ARM6, ARM7 and ARM8 are examples.

3. A varient on kernel as used to describe features built into a language as opposed to those provided by libraries.