The Collaborative International Dictionary of English v.0.48:

Heroic \He*ro"ic\, a. [F. h['e]ro["i]que, L. hero["i]cus, Gr.
   "hrwi:ko`s.]
   1. Of or pertaining to, or like, a hero; of the nature of
      heroes; distinguished by the existence of heroes; as, the
      heroic age; an heroic people; heroic valor.
      [1913 Webster]

   2. Worthy of a hero; bold; daring; brave; illustrious; as,
      heroic action; heroic enterprises.
      [1913 Webster]

   3. (Sculpture & Painting) Larger than life size, but smaller
      than colossal; -- said of the representation of a human
      figure.
      [1913 Webster]

   Heroic Age, the age when the heroes, or those called the
      children of the gods, are supposed to have lived.

   Heroic poetry, that which celebrates the deeds of a hero;
      epic poetry.

   Heroic treatment or Heroic remedies (Med.), treatment or
      remedies of a severe character, suited to a desperate
      case.

   Heroic verse (Pros.), the verse of heroic or epic poetry,
      being in English, German, and Italian the iambic of ten
      syllables; in French the iambic of twelve syllables; and
      in classic poetry the hexameter.

   Syn: Brave; intrepid; courageous; daring; valiant; bold;
        gallant; fearless; enterprising; noble; magnanimous;
        illustrious.
        [1913 Webster]

WordNet (r) 3.0 (2006):

heroic
    adj 1: very imposing or impressive; surpassing the ordinary
           (especially in size or scale); "an epic voyage"; "of
           heroic proportions"; "heroic sculpture" [syn: epic,
           heroic, larger-than-life]
    2: relating to or characteristic of heroes of antiquity; "heroic
       legends"; "the heroic age"
    3: having or displaying qualities appropriate for heroes; "the
       heroic attack on the beaches of Normandy"; "heroic explorers"
       [syn: heroic, heroical]
    4: of behavior that is impressive and ambitious in scale or
       scope; "an expansive lifestyle"; "in the grand manner";
       "collecting on a grand scale"; "heroic undertakings" [syn:
       expansive, grand, heroic]
    5: showing extreme courage; especially of actions courageously
       undertaken in desperation as a last resort; "made a last
       desperate attempt to reach the climber"; "the desperate
       gallantry of our naval task forces marked the turning point
       in the Pacific war"- G.C.Marshall; "they took heroic measures
       to save his life" [syn: desperate, heroic]
    n 1: a verse form suited to the treatment of heroic or elevated
         themes; dactylic hexameter or iambic pentameter [syn:
         heroic verse, heroic meter, heroic]

Moby Thesaurus II by Grady Ward, 1.0:

195 Moby Thesaurus words for "heroic":
   Alcaic, Anacreontic, Atlantean, Brobdingnagian, Castalian,
   Cyclopean, Gargantuan, Herculean, Homeric, Hudibrastic, Pierian,
   Pindaric, Theocritean, abysmal, acknowledged, admitted, alto,
   altruistic, astronomic, audacious, august, bardic, baritone, bass,
   big, bighearted, bold, bold-spirited, brave, bravura, bucolic,
   chivalric, chivalrous, choral, choric, classical, coloratura,
   colossal, conventional, courageous, customary, cyclopean, daring,
   dauntless, desperate, determined, didactic, distinguished,
   dithyrambic, doughty, dramatic, drastic, eclogic, elegiac,
   elephantine, elevated, eminent, enormous, epic, established,
   exaggerated, exalted, extravagant, extreme, fabulous, falsetto,
   famous, fearless, fixed, folk, gallant, generous, giant, giantlike,
   gigantic, glorious, godlike, grand, grandiose, great,
   great of heart, greathearted, hallowed, handed down, handsome,
   hardy, herolike, high, high-minded, hoary, honorable, huge, hymnal,
   idealistic, idyllic, immemorial, immense, infinite, intrepid,
   inveterate, ironhearted, jumbo, knightlike, knightly, largehearted,
   lauded, legendary, liberal, lionhearted, liturgical, lofty,
   long-established, long-standing, lyric, magnanimous, magnificent,
   magniloquent, majestic, mammoth, manful, manly, mighty, miraculous,
   mock-heroic, monster, monstrous, monumental, mountainous,
   mythological, narrative, noble, noble-minded, of long standing,
   of the folk, openhanded, operatic, oral, pastoral, plucky, poetic,
   poetico-mystical, poetico-mythological, poetico-philosophic,
   poetlike, prescriptive, princely, prodigious, profound, prominent,
   psalmic, psalmodial, psalmodic, renowned, rhapsodic, rooted, runic,
   sacred, sapphic, singing, skaldic, soaring, soldierlike, soldierly,
   soprano, stalwart, staunch, steadfast, stout, stouthearted,
   stupendous, sublime, superb, tenor, time-honored, titanic,
   towering, traditional, treble, tremendous, tried and true,
   true-blue, unafraid, undaunted, understood, unwritten, upstanding,
   valiant, valorous, vast, venerable, virile, virtuous, vocal,
   wonderful, worshipful