core1 W3 [countable]
the hard central part of a fruit such as an apple:
Remove the cores, and bake the apples for 40 minutes.
the most important or central part of something
most important part
a number of people who form a group which is very important to an organization: ➔ hard core
The business needs a new core of trained administrators.
a core group of clients
extremely or completely
shaken/shocked/thrilled to the core
When I heard the news, I was shaken to the core.
That woman is rotten to the core!
He was a bureaucrat to the core.
the central part of the Earth or any other planet
the central part of a nuclear reactor