The Collaborative International Dictionary of English v.0.48:

Obviation \Ob`vi*a"tion\, n.
   The act of obviating, or the state of being obviated.
   [1913 Webster]

WordNet (r) 3.0 (2006):

obviation
    n 1: the act of preventing something by anticipating and
         disposing of it effectively [syn: obviation,
         forestalling, preclusion]