fully aware and attentive; wide-awake; keen: She had an alert mind.
swift; agile; nimble.
an attitude of vigilance, readiness, or caution, as before an expected attack.
a warning or alarm of an impending military attack, a storm, etc.: We'd just boarded the bus when the alert sounded.
the period during which such a warning or alarm is in effect.
to warn (troops, ships, etc.) to prepare for action.
to warn of an impending raid, attack, storm, etc.: The radio alerted coastal residents to prepare for the hurricane.
to advise or warn; cause to be on guard: to alert gardeners to the dangers of some pesticides.
Idioms about alert
on the alert, on guard against danger; in readiness; vigilant: The state police are on the alert for an escaped convict believed to be in the area.
- a·lert·ly, adverb
- a·lert·ness, noun
- hy·per·a·lert, adjective
- un·a·lert·ed, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use alert in a sentence
The US Federal Bureau of Investigation became involved early on when the Tesla employee alerted it to Kriuchkov’s plan.
There's also an app—of course there's an app—that will alert you when the mask filters need to be replaced.LG’s battery-powered face mask will “make breathing effortless” | Ron Amadeo | August 27, 2020 | Ars Technica
The new $100 Inspire 2 activity tracker is different from the Halo, however, with a small screen that provides phone notifications and app alerts.Amazon jumps into smart wearables market with Halo activity tracking band | Aaron Pressman | August 27, 2020 | Fortune
Mobile phone and broadcast alerts advised people to prepare to evacuate.Improved three-week weather forecasts could save lives from disaster | Alexandra Witze | August 27, 2020 | Science News
District Attorney Michael Ramsey of Butte County, where Paradise is located, confirmed in March that PG&E alerted his office to the allegations and said he was awaiting further information.The Mystery House: How a Suspicious Multimillion Dollar Real Estate Deal Is Connected to California’s Deadliest Fire | by Scott Morris, Bay City News Foundation | August 26, 2020 | ProPublica
Minutes before an airplane hit the water, an alert would go out.Red Tape and Black Boxes: Why We Keep ‘Losing’ Airliners in 2014 | Clive Irving | December 29, 2014 | THE DAILY BEAST
France is on high alert this week after a series of attacks by loners.A Gift to the Jihadis: The Unseen Airport Security Threat | Clive Irving | December 27, 2014 | THE DAILY BEAST
I also want to alert you to the broader circumstances of my incarceration.An American Marine in Iran’s Prisons Goes on Hunger Strike | IranWire | December 18, 2014 | THE DAILY BEAST
Spoiler alert: Do not read if you haven't seen season five episode eight of The Walking Dead, “Coda”Norman Reedus on Motorcycles, Multitasking, And That Mid-Season Finale: “This Was A Rough One” | Oliver Jones | December 2, 2014 | THE DAILY BEAST
They walk closely together, tense, and alert in their movements.
It was Carmena, every nerve of her loyal nature on the alert to baffle this pursuer of Alessandro and Ramona.Ramona | Helen Hunt Jackson
Then, his hand resting on the handle of the cab-door, this expression suddenly changed to one of alert suspicion.Dope | Sax Rohmer
He is small, alert, brimful of jokes and of years; seventy they say, but he neither looks it nor acts it.Gallipoli Diary, Volume I | Ian Hamilton
But his eyes and ears were alert, and he was the first to hear the advent of a large body of horses along the main road.The Red Year | Louis Tracy
The almost lazy naturalness and simplicity faded gradually out of it, revealing the alert and seductive woman of the world.Bella Donna | Robert Hichens
British Dictionary definitions for alert
vigilantly attentive: alert to the problems
brisk, nimble, or lively
an alarm or warning, esp a siren warning of an air raid
the period during which such a warning remains in effect
on the alert
on guard against danger, attack, etc
watchful; ready: on the alert for any errors
to warn or signal (troops, police, etc) to prepare for action
to warn of danger, an attack, etc
- alertly, adverb
- alertness, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Other Idioms and Phrases with alert
see on the alert.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.