The Collaborative International Dictionary of English v.0.48:

Elusive \E*lu"sive\, a.
   Tending to elude; using arts or deception to escape; adroitly
   escaping or evading; eluding the grasp; fallacious.
   [1913 Webster]

         Elusive of the bridal day, she gives
         Fond hopes to all, and all with hopes deceives. --Pope.
   -- E*lu"sive*ly, adv. -- E*lu"sive*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

elusiveness
    n 1: the quality of being difficult to grasp or pin down; "the
         author's elusiveness may at times be construed as
         evasiveness"