A red flag serves as a warning.
red flag definition by Webster's New World
- a warning flag
- Informal something serving as a warning of trouble or danger ahead
- Informal something that arouses anger, irritation, revolt, etc.
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
red flag definition by American Heritage Dictionary
- A warning signal.
- Something that demands attention or provokes an irritated reaction.