The Collaborative International Dictionary of English v.0.48:

Inevitability \In*ev`i*ta*bil"i*ty\, n. [Cf. F.
   in['e]vitabilit['e].]
   Impossibility to be avoided or shunned; inevitableness.
   --Shelford.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inevitability
    n 1: the quality of being unavoidable [syn: inevitability,
         inevitableness]