red alert

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. Compare blue alert, white alert, yellow 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.

Word History and Origins

Origin of red alert¹

First recorded in 1960–65

Example Sentences

Emergency management officials issued a red alert after scientists observed tremors on the island’s only active volcano that indicated a heightened risk of eruption as magma broke up rocks and moved near the surface.

From Washington Post

Perhaps by then, scientists will be able to give earlier red alerts to warn of an incoming storm, giving more time to move satellites, buttress transformers and stave off the worst.

From Science News

Red Alert, which alerts users every time a rocket is fired into Israel, has already been downloaded 780,000 times.

From The Daily Beast

Despite the detractors, Red Alert has become so ubiquitous that even the government is aware of it.

From The Daily Beast

Seeking much-needed peace of mind, she downloaded Red Alert, an app that goes off every time a rocket is fired into Israel.

From The Daily Beast

This was the fourth straight day of red-alert sirens wailing in Tel Aviv, and we were getting used to it.

From The Daily Beast

A little later, waiting for a friend outside a local bar, I thought about where I would run to if another red alert sounded.

From The Daily Beast

When the red alert flashed on throughout the ship it brought the others hurrying to the control cabin.

From Project Gutenberg