The Collaborative International Dictionary of English v.0.48:

Fearless \Fear"less\, a.
   Free from fear.

   Syn: Bold; daring; courageous; intrepid; valorous; valiant;
        brave; undaunted; dauntless; heroic. -- Fear"less*ly,
        adv. -- Fear"less*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

fearless
    adj 1: oblivious of dangers or perils or calmly resolute in
           facing them [syn: unafraid(p), fearless] [ant:
           afraid(p)]
    2: 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:

34 Moby Thesaurus words for "fearless":
   assured, audacious, aweless, bold, brave, chivalrous, confident,
   courageous, daring, dauntless, dreadless, gallant, game, heroic,
   intrepid, lionhearted, plucky, sanguine, sure, unafraid,
   unapprehensive, unbashful, undiffident, unfearful, unfearing,
   unfrightened, unscared, unshy, unterrified, untimid, untimorous,
   valiant, valorous, venturesome