Source : Webster's Revised Unabridged Dictionary (1913)

Unseat \Un*seat"\, v. t. [1st pref. un- + seat.]
   1. To throw from one's seat; to deprive of a seat. --Cowper.

   2. Specifically, to deprive of the right to sit in a
      legislative body, as for fraud in election. --Macaulay.

Source : WordNet®

unseat
     v 1: remove from political office; "The Republicans are trying to
          unseat the liberal Democrat"
     2: dislodge from one's seat, as from a horse