warner Definition

warn
verb warned, warning

1. To make them aware of (possible or approaching danger or difficulty).

Thesaurus: caution, alert, put on one's guard, counsel, advise, apprise, notify, inform, tip off (slang).
Form: warn someone of something (usually)
Form: warn someone about something
2. To advise someone strongly.
3. To rebuke or admonish someone, with the threat of punishment for a repetition of the offence.
4. To caution them.

Form: warn someone against someone (often)
Form: warn someone against something
5. To inform someone in advance.

Example: warned him she might be late

Derivative: warner
noun

Etymology: Anglo-Saxon wearnian.

Phrasal Verb: warn someone off

To order them to go or keep away, often with threats.