From Longman Dictionary of Contemporary Englishhard coreˈhard core noun [singular] British English a) GROUP OF PEOPLEthe small group of people that are most active within a group or organization the hard core of the Communist Party b) GROUP OF PEOPLEa 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.
Examples from the Corpus
hard core• Others are on the run with their families, leaving a hard core to take their guns and guard their property.• But while Corden thanked the loyal hard core, he did not criticise the floating fans.hard-coreˌhard-core, hardcore /ˈhɑːdkɔː $ ˈhɑːrdkɔːr/ adjective 1 [only before noun]EXTREME having an extreme way of life or an extreme belief that is very unlikely to change a hard-core drug addict hard-core racists2 → hard-core pornographyExamples from the Corpus
hard-core• We asked for 355 million new dollars to treat hard-core addicts.• More likely than not, many of the seats are filled by hard-core fans who are zealous about the sport.• A few days later Anderson talked with three of the hard-core leaders.• After their tour, Anderson and the camp commandant arranged for the white officials to meet some of the hard-core men.• The main reason is, employers can pick out and fire all the hard-core pro-union workers.• It was to be 24 days before the last hard-core protesters gave themselves up.• But Dole will have the support of loyal, hard-core Republicans.• Investigations of a hereditary or hard-core social problem group have always been crucial in conservative social reformist strategies.From Longman Business Dictionaryhard coreˈhard core noun [countable usually singular] those who are most involved or active in something, or who support something very stronglyThere is a hard core of users for videoconferencing, but it is certainly not a mass medium. 