The Collaborative International Dictionary of English v.0.48:

Adventuresome \Ad*ven"ture*some\, a.
   Full of risk; adventurous; venturesome. --
   Ad*ven"ture*some*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

adventuresome
    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]