The Collaborative International Dictionary of English v.0.48:

Colonization \Col`o*ni*za"tion\, n. [Cf. F. colonisation.]
   The act of colonizing, or the state of being colonized; the
   formation of a colony or colonies.
   [1913 Webster]

         The wide continent of America invited colonization.
                                                  --Bancroft.
   [1913 Webster]

WordNet (r) 3.0 (2006):

colonization
    n 1: the act of colonizing; the establishment of colonies; "the
         British colonization of America" [syn: colonization,
         colonisation, settlement]

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "colonization":
   Hare system, PR, absentee voting, adoption, anchorage,
   appropriation, arrogation, assumption, ballot-box stuffing,
   card voting, conquest, cumulative system, cumulative voting,
   election fraud, empeoplement, enslavement, establishment, fixation,
   floating, foundation, inauguration, indent, inhabiting, initiation,
   installation, installment, investiture, list system, lodgment,
   mooring, occupation, peoplement, peopling, plantation,
   plural system, population, preemption, preferential system,
   preferential voting, preoccupation, prepossession,
   proportional representation, proxy voting, repeating, requisition,
   settlement, settling, single system, single transferrable vote,
   single-member district, subjugation, takeover, taking over,
   usurpation, vote, voting, voting machine