un- + seat
unseat (third-person singular simple present unseats, present participle unseating, simple past and past participle unseated)
- To throw from one's seat; to deprive of a seat.
The frightened horse reared up and unseated its rider.
- To deprive of the right to sit in a legislative body, as for fraud in election, or simply by defeating them in an election.
Having lost her seat to a Tory, she succeeded in unseating him in the next general election.