The Collaborative International Dictionary of English v.0.48:

Venturesome \Ven"ture*some\, a.
   Inclined to venture; not loth to run risk or danger;
   venturous; bold; daring; adventurous; as, a venturesome boy
   or act. -- Ven"ture*some*ly, adv. -- Ven"ture*some*ness,
   n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

venturesomeness
    n 1: the trait of being adventurous [syn: adventurousness,
         venturesomeness]