"Usurp" redirects here. You might be also looking for Changing username/Usurpations.Usurper (lat. usurpare = to seize for use, to use) is a derogatory term used to describe either an illegitimate or controversial claimant to the throne in a monarchy, or a person who succeeds in establishing himself as a monarch without inheriting the throne, or any other person exercising authority unconstitutionally. It may also be applied to an official acting ultra vires, outside his authority or jurisdiction