Source : Webster's Revised Unabridged Dictionary (1913)

Centralism \Cen"tral*ism\, n.
   1. The state or condition of being central; the combination
      of several parts into one whole; centralization.

   2. The system by which power is centralized, as in a
      government.

Source : WordNet®

centralism
     n : the political policy of concentrating power in a central
         organization