[hard core] n (1936) 1: a central or fundamental and usu. enduring group or part: as a: a relatively small enduring core of society marked by apparent resistance to change or inability to escape a persistent wretched condition (as poverty or chronic unemployment) b: a militant or fiercely loyal faction
2. usu hard.core chiefly Brit: hard material in pieces (as broken bricks or stone) used as a bottom (as in making roads and in foundations)