To dupe someone means to trick or fool them into believing something false. When a con artist dupes a victim, they deceive them cleverly, often making the lie seem believable. A student might get duped by a fake website that looks real but contains wrong information, or a friend might dupe you into thinking school was cancelled as an April Fools' joke.

The word carries a sense of being outsmarted or misled, usually because someone took advantage of trust. If you're duped, you believed something that turned out to be false, and someone deliberately made that happen. A newspaper that publishes false information has been duped by its source.

As a noun, a dupe is the person who gets tricked. The poor dupe believed everything the scammer told him. This meaning can suggest someone gullible or naive, though anyone can be duped by a clever enough deception. The key is that duping involves intentional deception, not just an honest misunderstanding. When you realize you've been duped, that uncomfortable feeling comes from knowing someone deliberately fooled you.