The Collaborative International Dictionary of English v.0.48:

Centralize \Cen"tral*ize\, v. t. [imp. & p. p. Centralized; p.
   pr. & vb. n. Centralizing.] [Cf. F. centraliser.]
   To draw or bring to a center point; to gather into or about a
   center; to bring into one system, or under one control.
   [1913 Webster]

         [To] centralize the power of government. --Bancroft.
   [1913 Webster]

WordNet (r) 3.0 (2006):

centralize
    v 1: make central; "The Russian government centralized the
         distribution of food" [syn: centralize, centralise,
         concentrate] [ant: decentralise, decentralize,
         deconcentrate]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "centralize":
   affiliate, ally, approach, associate, band together, be in cahoots,
   bunch, bunch up, cabal, cement a union, center, center on,
   center round, close, close in, close up, close with, club,
   club together, come together, concenter, concentralize,
   concentrate, confederate, consociate, conspire, converge, couple,
   fall in with, federalize, federate, funnel, gang, gang up,
   go in partners, go in partnership, hook up with, intersect,
   join forces, join fortunes with, join together, join up with,
   join with, league, marry, meet, middle, narrow the gap, nip,
   organize, pair, pair off, partner, pinch, run together,
   stand together, stand up with, taper, team up with, team with,
   throw in with, tie in with, tie up with, unionize, unite,
   unite with, wed