A physical or verbal attack meant to serve as a warning that strong action will be taken if a person does not stop doing something or change their behaviour. The bow is the rounded forward part of a ship on both sides, which meet at the prow, which is the very front end or tip of a vessel. A shot across the bows derives from the naval practice of firing a harmless cannon shot across the bows of an opponent’s ship as a signal that they should stop, letting them know they will be attacked unless they surrender immediately.