1the tough central part of various fruits, containing the seeds:an apple core
2the part of something that is central to its existence or character:the plan has the interests of children at its core [as modifier]:managers can concentrate on their core activities
an important or unchanging group of people forming the central part of a larger body:a flexible core of permanent employees
3the dense central region of a planet, especially the nickel-iron inner part of the earth.
the central part of a nuclear reactor, which contains the fissile material.
a tiny ring of magnetic material used in a computer memory to store one bit of data, now superseded by semiconductor memories.
the inner strand of an electric cable or rope.
the muscles of the torso, especially the lower back and abdominal area, which assist in the maintenance of good posture, balance, etc.:nothing will strengthen your core like balancing a heavy barbell on your back or lifting one off the floor [as modifier]:the core muscles of the abdomen
a piece of soft iron forming the centre of an electromagnet or an induction coil.
an internal mould filling a space to be left hollow in a casting:bronzes that have been cast using a clay core
a cylindrical sample of rock, ice, or other material obtained by boring with a hollow drill.
Archaeology a piece of flint from which flakes or blades have been removed.
remove the tough central part and seeds from (a fruit):peel and core the pears
to the core
to the depths of one’s being:she was shaken to the core by his words
used to indicate that someone possesses a characteristic to a very high degree:he is a politician to the core