ˈhard core noun [singular] British English
a) the small group of people that are most active within a group or organization:
the hard core of the Communist party
b) a group of people who cannot be persuaded to change their behaviour or beliefs:
There is still a small hard core of football supporters who cause trouble whenever they can.

[TahlilGaran] Dictionary of Contemporary English ▲

ˌhard-core , hard‧core /ˈhɑːdkɔː $ ˈhɑːrdkɔːr/ adjective

1. [only before noun] having an extreme way of life or an extreme belief that is very unlikely to change:
a hard-core drug addict
hard-core racists

2. hard-core pornography magazines, films etc that show the details of sexual behaviour, often in an unpleasant way

[TahlilGaran] Dictionary of Contemporary English ▲