signalflag
nounUK /ˈsɪɡnəl flæɡ/
US /ˈsɪɡnəl flæɡ/
A signal flag is a colored flag that people wave or show to send a message to someone far away.
The sailor raised a signal flag to tell the other boats to come back to shore.
OTHER MEANINGS
2. A flag used in a system of flags to spell out letters or words, especially at sea.
Each signal flag stands for a different letter in the code.
3. A flag waved by a person to direct traffic, trains, or aircraft.
The worker used a signal flag to guide the plane to its parking spot.
4. A small flag used in sports or racing to give instructions to players or drivers.
The marshal waved a signal flag to warn the drivers about the slippery track.