The Collaborative International Dictionary of English v.0.48:

Adventurous \Ad*ven"tur*ous\, a. [OE. aventurous, aunterous, OF.
   aventuros, F. aventureux, fr. aventure. See Adventure, n.]
   1. Inclined to adventure; willing to incur hazard; prone to
      embark in hazardous enterprise; rashly daring; -- applied
      to persons.
      [1913 Webster]

            Bold deed thou hast presumed, adventurous Eve.
                                                  --Milton.
      [1913 Webster]

   2. Full of hazard; attended with risk; exposing to danger;
      requiring courage; rash; -- applied to acts; as, an
      adventurous undertaking, deed, song.
      [1913 Webster]

   Syn: Rash; foolhardy; presumptuous; enterprising; daring;
        hazardous; venturesome. See Rash.
        [1913 Webster]

WordNet (r) 3.0 (2006):

adventurous
    adj 1: willing to undertake or seeking out new and daring
           enterprises; "adventurous pioneers"; "the risks and gains
           of an adventuresome economy" [syn: adventurous,
           adventuresome] [ant: unadventurous]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "adventurous":
   adventuresome, adversary, aggressive, aleatory, ambitious,
   antagonist, anti, assaulter, attacker, audacious, bold, brash,
   brave, chancy, con, courageous, daredevil, daring, death-defying,
   devil-may-care, dicey, doughty, driving, dynamic, enterprising,
   fire-eating, foolhardy, forceful, forward, full of risk, go-ahead,
   harebrained, hazardous, hotheaded, hustling, impetuous, imprudent,
   intrepid, madbrain, madbrained, madcap, match, opposer, oppugnant,
   overbold, overconfident, presumptuous, pushful, pushing, pushy,
   rash, reckless, riskful, risky, speculative, temerarious,
   up-and-coming, venturesome, venturous, wild, wild-ass, wildcat