The Collaborative International Dictionary of English v.0.48:

decentralization \de*cen`tral*i*za"tion\, n.
   1. The action of decentralizing, or the state of being
      decentralized. "The decentralization of France." --J. P.
      Peters.
      [1913 Webster]

   2. the spread of power away from the center to local branches
      or governments.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

decentralization
    n 1: the social process in which population and industry moves
         from urban centers to outlying districts [syn:
         decentralization, decentalisation]
    2: the spread of power away from the center to local branches or
       governments [syn: decentralization, decentralisation]
       [ant: centralisation, centralization]