The Collaborative International Dictionary of English v.0.48:

dauntless \daunt"less\, a.
   Incapable of being daunted; undaunted; bold; fearless;
   intrepid.
   [1913 Webster]

         Dauntless he rose, and to the fight returned. --Dryden.
   -- Daunt"less*ly, adv. -- Daunt"less*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dauntless
    adj 1: invulnerable to fear or intimidation; "audacious
           explorers"; "fearless reporters and photographers";
           "intrepid pioneers" [syn: audacious, brave,
           dauntless, fearless, hardy, intrepid,
           unfearing]

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "dauntless":
   audacious, aweless, bold, brave, confident, courageous, daring,
   dreadless, fearless, gallant, game, gritty, gutsy, gutty, heroic,
   indomitable, intrepid, invincible, lionhearted, mettlesome, plucky,
   spunky, stalwart, unafraid, unapprehensive, unbashful,
   unconquerable, undaunted, undiffident, unfearful, unfearing,
   unflinching, unfrightened, unscared, unshy, unterrified, untimid,
   untimorous, valiant, valorous, venturesome