hard core

hard core
    n 1: the most dedicated and intensely loyal nucleus of a group
         or movement
    

49 Moby Thesaurus words for "hard core":
      adamant, adamantine, ardent, cast-iron, dour, fanatic, fiery, firm,
      flaming, flinty, grim, hard, heated, hot, hotheaded, immovable,
      immutable, implacable, impliable, inelastic, inexorable, inflamed,
      inflexible, intransigent, iron, irreconcilable, madcap, passionate,
      red-hot, relentless, rigid, rigorous, rock-ribbed, scorching,
      steely, stern, stiff, totally committed, unaffected, unalterable,
      unbending, unchangeable, uncompromising, ungiving, unmoved,
      unrelenting, unyielding, white-hot, zealous