The Collaborative International Dictionary of English v.0.48:

Lion-hearted \Li"on-heart`ed\ (l[imac]"[u^]n*h[aum]rt`[e^]d), a.
   Very brave; brave and magnanimous. --Sir W. Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lionhearted
    adj 1: extraordinarily courageous

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "lionhearted":
   bold, bold-spirited, brave, chivalric, chivalrous, courageous,
   dauntless, doughty, fearless, gallant, greathearted, hardy, heroic,
   herolike, intrepid, ironhearted, knightlike, knightly, manful,
   manly, soldierlike, soldierly, stalwart, stout, stouthearted,
   unafraid, undaunted, valiant, valorous