The Collaborative International Dictionary of English v.0.48:

Valiant \Val"iant\, a. [OE. valiant, F. vaillant, OF. vaillant,
   valant, originally p. pr. of OF. & F. valoir to be worth, L.
   valere to be strong. See Wield, and cf. Avail,
   Convalesce, Equivalent, Prevail, Valid.]
   [1913 Webster]
   1. Vigorous in body; strong; powerful; as, a valiant fencer.
      [Obs.] --Walton.
      [1913 Webster]

   2. Intrepid in danger; courageous; brave.
      [1913 Webster]

            A valiant and most expert gentleman.  --Shak.
      [1913 Webster]

            And Saul said to David . . . be thou valiant for me,
            and fight the Lord's battles.         --1 Sam.
                                                  xviii. 17.
      [1913 Webster]

   3. Performed with valor or bravery; heroic. "Thou bearest the
      highest name for valiant acts." --Milton.
      [1913 Webster]

            [The saints] have made such valiant confessions.
                                                  --J. H.
                                                  Newman.
      [1913 Webster] -- Val"iant*ly, adv. -- Val"iant*ness,
      n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

valiant
    adj 1: having or showing valor; "a valiant attempt to prevent
           the hijack"; "a valiant soldier" [syn: valiant,
           valorous]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "valiant":
   Achilles, David, Hector, Roland, Samson, a man, audacious, bold,
   bold-spirited, brave, bulldog, chivalric, chivalrous, chutzpanik,
   courageous, dauntless, decorated hero, demigod, demigoddess,
   doughty, fearless, fighting cock, gallant, gamecock, good soldier,
   greathearted, hardy, hero, heroic, heroine, herolike, intrepid,
   ironhearted, knightlike, knightly, lion, lionhearted,
   man of courage, manful, manly, paladin, soldierlike, soldierly,
   stalwart, stout, stouthearted, the brave, tiger, undaunted,
   valiant knight, valorous