From Longman Dictionary of Contemporary Englishunseatun‧seat /ʌnˈsiːt/ verb [transitive] 1 BEAT/DEFEATto remove someone from a powerful job or position an attempt to unseat the party leader2 DSHif a horse unseats someone, it throws them off its back→ See Verb table
Examples from the Corpus
unseat• As the horse buckled, Bellerophon was unseated and fell to earth.• In November, Sweeney failed to unseat Congressman Jim Kolbe.• And he will probably try to rally the formidable and disgruntled forces of the opposition to destabilise and unseat Mr Sharif.• She hopes to exploit the preferential voting system in the federal elections to unseat the ruling coalition.• Still later, one more attempt was made to unseat Zeus: the Giants rebelled. 