To do something illegitimately means to do it in a way that breaks the rules, violates the law, or isn't properly authorized. When a government official acts illegitimately, they're using their power in ways they're not supposed to. When someone claims a prize illegitimately, they didn't actually earn or win it fairly.

Illegitimately describes actions that lack proper authority or violate established standards.

In everyday situations, a student who illegitimately gets credit for a group project might have put their name on work they didn't actually do. A player who wins a tournament illegitimately might have broken the competition rules without getting caught. The word emphasizes that something happened through improper means, even if it appeared correct on the surface.

The word carries serious weight. Unlike simply making a mistake or bending minor rules, acting illegitimately suggests deliberately operating outside proper boundaries. When historians say a ruler came to power illegitimately, they mean that person seized control without the legal right to do so.