core

(noun) a small group of indispensable persons or things. Synonyms: nucleus, core group. Examples: "Five periodicals make up the core of their publishing program."

(noun) the center of an object. Examples: "The ball has a titanium core."

(noun) the central part of the Earth.

(noun) the choicest or most essential or most vital part of some idea or experience. Synonyms: kernel, substance, center, centre, essence, gist, heart, heart and soul, inwardness, marrow, meat, nub, pith, sum, nitty-gritty. Examples: "The gist of the prosecutor's argument." "The heart and soul of the republican party." "The nub of the story."

(noun) a cylindrical sample of soil or rock obtained with a hollow drill.

(noun) an organization founded by James Leonard Farmer in 1942 to work for racial equality. Synonyms: Congress of Racial Equality, CORE.

(noun) the central meaning or theme of a speech or literary work. Synonyms: effect, essence, burden, gist.

(noun) (computer science) a tiny ferrite toroid formerly used in a random access memory to store one bit of data; now superseded by semiconductor memories. Synonyms: magnetic core. Examples: "Each core has three wires passing through it, providing the means to select and detect the contents of each bit."

(noun) the chamber of a nuclear reactor containing the fissile material where the reaction takes place.

(noun) a bar of magnetic material (as soft iron) that passes through a coil and serves to increase the inductance of the coil.

(verb) remove the core or center from. Examples: "Core an apple."