1the tough central part of various fruits, containing the seeds:an apple core
2the central or most important part of something, in particular.
[often as modifier] the part of something that is central to its existence or character:managers can concentrate on their core activitiesthe plan has the interests of children at its core
an important or unchanging group of people forming the central part of a larger body.
the 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.
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a tiny ring of magnetic material used in a computer memory to store one bit of data, now superseded by semiconductor memories.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 electrical cable or rope.
a piece of soft iron forming the center of an electromagnet or an induction coil.
an internal mold filling a space to be left hollow in a casting.
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