unhorse

verb (used with object), un·horsed, un·hors·ing.

1. to cause to fall from a horse, as in battle; dislodge from the saddle: Sir Gawain unhorsed the strange knight.
2. to defeat; overcome; dislodge, as from a position or office: His vigorous campaign unhorsed his adversary.

verb (tr)

1. (usually passive) to knock or throw from a horse
2. to overthrow or dislodge, as from a powerful position
3. rare to unharness horses from (a carriage, etc)

v.late 14c., “to throw (someone) from his horse,” from un- (2) + horse (v.). Cf. Middle Dutch ontorsen.