Used when someone's well-being could be at risk, and you want to prevent harm. Signs were posted to warn off swimmers from the rough sea.
Pro Tip 2/3
Authority Figure
Often uttered by someone in charge or with responsibility, like a parent or official. The lifeguard warned off the kids from getting too close to the deep end.
Pro Tip 3/3
Property Boundaries
Use this when mentioning someone should not enter a private area or property. The farmer warned off hikers from wandering onto his land.