hard-core (Adjective) — Intensely loyal. ex. "his hard-core supporters"
hard-core (Adjective) — Stubbornly resistant to change or improvement. ex. "hard-core addicts"
hard-core (Adjective) — Extremely explicit. ex. "hard-core pornography"
hard-core (Noun) — The most dedicated and intensely loyal nucleus of a group or movement.