A person who takes things from one place to another place secretly and illegally.
A smuggler is usually thought of as a bad person who does illegal things.
Examples:
The smuggler took the treasure across the border.
The police caught the smuggler with the stolen goods.
The smuggler hid the things in a secret place.
The smuggler was sneaky and tried to hide from the police.
The smuggler was so good at hiding things, no one ever found out.
The smuggler was very rich from selling the things he brought.