A usurper is someone who seizes power or takes a position that doesn't rightfully belong to them, usually by force or deception. The word comes from situations where someone grabs a throne, title, or authority they have no legal claim to.

The word carries a strongly negative feeling. Nobody calls themselves a usurper; it's what others call you when they believe you've stolen something that wasn't yours to take. A legitimate successor who inherits a throne isn't a usurper, even if some people disagree with the inheritance rules. But someone who uses violence, trickery, or betrayal to grab power is.

You might hear the word in non-royal contexts too. If someone takes credit for another person's idea at school or work, they're usurping recognition that belonged to someone else. The core meaning stays the same: taking something you have no right to, usually through underhanded means.