Definitions of core:

• noun:   a bar of magnetic material (as soft iron) that passes through a coil and serves to increase the inductance of the coil
• noun:   the chamber of a nuclear reactor containing the fissile material where the reaction takes place
• noun:   a small group of indispensable persons or things

  Example: "Five periodicals make up the core of their publishing program"

• noun:   the center of an object

  Example: "The ball has a titanium core"

• noun:   the central part of the Earth
• 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
• noun:   the choicest or most essential or most vital part of some idea or experience
• noun:   the central meaning or theme of a speech or literary work
• verb:   remove the core or center from

  Example: "Core an apple"

• name:  A surname (rare: 1 in 50000 families; popularity rank in the U.S.: #7344)