Caution is great care which you take in order to avoid possible danger.

If someone cautions you, they warn you about problems or danger.

If someone who has broken the law is cautioned by the police, they are warned that if they break the law again official action will be taken against them.

If someone who has been arrested is cautioned, the police warn them that anything they say may be used as evidence in a trial.

If you throw caution to the wind, you behave in a way that is not considered sensible or careful.