Gullible (adjective)

Easily deceived or cheated.

Origin:

The word "gullible" comes from the word "gull" which means a person who is easily deceived.

Examples:

1. He was so gullible that he believed everything I said.
2. Don't be so gullible, always question what you are told.
3. She had a reputation for being gullible.
4. He was taken advantage of because he was gullible.
5. He was a gullible person, always believing in others lies.