Definition of red flag

The phrase "raising a red flag" is a figurative expression that originated in horse racing. In the early 19th century, a red flag was raised as a warning when a horse was lame or injured during a race, signaling to other jockeys to withdraw their horses and avoid crossing the finish line. The use of the red flag in racing was later extended to other sports, such as sailing and cycling, as a warning of potential danger. It gradually became a metaphor for identifying a potential problem or danger, particularly in situations where swift action is necessary to avoid negative consequences. The phrase "red flag" was first recorded in print in 1868, and by the early 20th century, it had gained widespread usage as a warning symbol in various contexts, such as signaling danger in mines, factories, and construction sites. Today, "raising a red flag" is commonly used to describe any situation or issue that poses a potential threat or danger, requiring prompt attention and action to prevent negative outcomes.