What is Core ?
Core is (noun) the central part the core of an apple, an apple core the hard part in the middle of an apple, containing the seeds He threw the apple core into the lake. rotten to the core completely bad The local police force is rotten to the core. to take a core sample to cut a long round piece of soil or rock for testing(verb) to take out the central part of a fruit such as an apple Peel and core the apples before putting them in the oven.
source: Easier English, Student Dictionary Upper Intermediate Level