noun ( BrE )
1.
[ sing.+ sing./pl. v . ] the small central group in an organization, or in a particular group of people, who are the most active or who will not change their beliefs or behaviour :
It's really only the hard core that bother(s) to go to meetings.
A hard core of drivers ignores the law.
2.
[ U ] (usually ˈhardcore ) small pieces of stone, brick, etc. used as a base for building roads on