red flag

¹ American  

noun

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. Also called powder flag.  Nautical. 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. (initial capital letters) 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.

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red-flag ² American  

[red-flag] / ˈrɛdˈflæg /

verb (used with object)

red-flagged, red-flagging

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.

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adjective

1. of or relating to a red flag.

2. intended or serving to emphasize, warn, incite, or provoke.

red flag ¹ British  

noun

1. a symbol of socialism, communism, or revolution

2. a warning of danger or a signal to stop

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Red Flag ² British  

noun

1. a socialist song, written by James Connell (1852–1929), Irish political activist, in 1889

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Etymology

Origin of red flag¹

First recorded in 1770–80

Origin of red-flag²

First recorded in 1880–85

Example Sentences

In theory, those developments pose a red flag for a central bank tasked with keeping inflation at 2%.

From The Wall Street Journal

Drivers had to burn gas to find gas, creeping from station to station, looking for the green flags that meant “open,” not the red flags that signaled “closed” or “out of gas.”

From Los Angeles Times

That particular slide has been passed around on social media lately by critics who see ARR as a major red red flag in the private-credit bear case.

From Barron's

The disparity raises a red flag, said New York University professor Anna Harvey, who noted that 60% to 70% of crime isn’t reported to police.

From The Wall Street Journal

It is difficult to name the red flags which might signal a woman will regret her decision to pursue motherhood, caveats O'Connor, because everyone's experience is unique.

From BBC