red flag

US: (red′flag′)

Inflections of 'red flag' (v): (⇒ conjugate)

red-flags

v 3rd person singular

red-flagging

v pres p

red-flagged

v past

red-flagged

v past p

WordReference Random House Unabridged Dictionary of American English © 2026

red′ flag′, 

1. the symbol or banner of a left-wing revolutionary party.
2. a danger signal.
3. something that provokes an angry or hostile reaction:
   The talk about raising taxes was a red flag to many voters.
4. Nautical, Naval Terms Also called powder flag. a red burgee, designating in the International Code of Signals the letter "B,'' flown by itself to show that a vessel is carrying, loading, or discharging explosives or highly inflammable material.
5. Military (caps.) a war game the U.S. Air Force holds several times each year at Nellis Air Force Base, Nevada, to train personnel in air combat.
• 1770–80

red-flag  (red′flag′), v., -flagged, -flag•ging, adj. 
v.t. 

1. to mark or draw attention to for a particular purpose:
   The department has red-flagged the most urgent repair work to be done.
2. to provoke the attention of;
   alert;
   arouse:
   The animal's refusal to eat red-flagged the keeper that something was wrong.

adj. 

3. of or pertaining to a red flag.
4. intended or serving to emphasize, warn, incite, or provoke.

• 1880–85

Collins Concise English Dictionary © HarperCollins Publishers::

red flag noun

1. a symbol of socialism, communism, or revolution
2. a warning of danger or a signal to stop