What does the idiom “shot across the bow” mean?
A shot across the bow is a warning against continuing with a course of action.
For example :
“The bombing raid was a shot across the bow, warning of more serious military action later.”
“Let’s file a complaint with regulators about their sales techniques. That’ll be a shot across the bow. If they don’t stop, we’ll go ahead with the lawsuit.”
The idiom comes from naval combat; the bow (rhymes with cow) is the front part of a ship, so a shot fired across the bow is a warning not to continue farther.