Source : Webster's Revised Unabridged Dictionary (1913)

Annexation \An`nex*a"tion\, n. [Cf. F. annexation. See {Annex},
   v. t.]
   1. The act of annexing; process of attaching, adding, or
      appending; the act of connecting; union; as, the
      annexation of Texas to the United States, or of chattels
      to the freehold.

   2.
      (a) (Law) The union of property with a freehold so as to
          become a fixture. Bouvier.
      (b) (Scots Law) The appropriation of lands or rents to the
          crown. --Wharton.

Source : WordNet®

annexation
     n 1: incorporation by joining or uniting [syn: {appropriation}]
     2: the formal act of acquiring something (especially territory)
        by conquest or occupation; "the French annexation of
        Madagascar as a colony in 1896"; "a protectorate has
        frequently been a first step to annexation"