A gullible person believes things too easily, even when they should be more careful or skeptical. If someone tells you they can sell you the Brooklyn Bridge for twenty dollars, or that they've trained their goldfish to do algebra, and you believe them right away without thinking it through, you're being gullible.

Being gullible means you trust what people say without asking enough questions or looking for evidence. A gullible student might believe a classmate who claims homework has been canceled when it really hasn't. Someone gullible might fall for pranks repeatedly, like believing that pushing a door marked “push” will unlock a secret passage.

The word isn't quite the same as being trusting or optimistic. Trust can be a good quality when it's earned, but gullibility means accepting things without thinking critically about whether they make sense. A gullible person might hand over their lunch money because someone said it's a new school rule, while a thoughtfully trusting person would check with a teacher first.

Scammers and pranksters look for gullible people because they're easier to fool. Learning to ask good questions like “Does this make sense?” or “How do you know that's true?” helps protect you from being taken advantage of. Everyone can be fooled sometimes, but staying curious and thinking carefully about what you hear makes you much harder to trick.