What does annexation mean?
The definition of annexation
An`nex*a”tion, n.
Etym: [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.

(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.