impostor
n. countablen. someone who pretends to be a different person or to have a different identity. You use this when someone lies about who they are to trick others.
n. a person who assumes a false identity or pretends to be someone else. Often used in the context of social engineering or psychological conditions where the individual believes they are not who they are.
The police arrested the impostor who tried to enter the building.
The impostor used a stolen passport to board the flight and was only caught after the pilot noticed the mismatched photo.
In the classic psychological study, the subject began to believe he was an impostor, convinced that his entire life was a series of borrowed identities rather than a genuine existence.
Borrowed from Middle French imposteur, respelled in the Latin manner; ultimately from Latin impositor, agent form of Latin imponere (“to impose”).