red alert

American  

noun

1. (in military or civilian defense) the most urgent form of alert, signaling that an enemy attack is believed to be imminent.

2. the signal or alarm sounded for this alert.

3. a signal or warning that a critical situation is developing or has occurred.

4. the period during which a state of crisis or danger is declared to exist.

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Etymology

Origin of red alert

First recorded in 1960–65

Example Sentences

And earlier this month, First Minister John Swinney confirmed that a red alert had been issued for one of the wards at the hospital.

From BBC • Mar. 16, 2026

The army has been deployed to help with evacuations amid a red alert for more heavy rainfall this week.

From BBC • Feb. 5, 2026

And when Google released its latest model to positive reactions, Altman issued a "red alert," urging OpenAI teams to give ChatGPT their best efforts.

From Barron's • Dec. 16, 2025

Understandably therefore, the officials are on red alert, desperate to ensure any dangerous tackles or collisions don't slip through the net.

From BBC • Nov. 25, 2025

For the kill shot, I posted it and Crew Chrissie with a blinking red alert on the Brandywine Hollows HS community page, which the teachers and administrators checked all the time.

From "Burning Blue" by Paul Griffin