\ ə-ˈlərt How to pronounce alert (audio) \

Definition of alert

 (Entry 1 of 3)

1a : watchful and prompt to meet danger or emergency an alert guard trying to stay alert to possible problems
b : quick to perceive and act mentally alert
2 : active, brisk elicited an alert response



Definition of alert (Entry 2 of 3)

1 : a state of careful watching and readiness especially for danger or opportunity on 24-hour alert
2a : an alarm or other signal of danger traffic alerts They sounded the alert.
b : an urgent notice … an alert to parents … about new immunization requirements.— Ann Schrader
3 : the period during which an alert is in effect
on the alert
: looking for or expecting something (such as danger or an opportunity) Drivers need to be on the alert for icy condition. always on the alert for a good bargain


alerted; alerting; alerts

Definition of alert (Entry 3 of 3)

transitive verb

1 : to call (someone) to a state of readiness : warn alerted the school board of a possible teachers' strike alert the authorities
2 : to make (someone) aware of something alerted the public to the dangers of pesticides

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Other Words from alert


alertly adverb
alertness noun

Synonyms & Antonyms for alert

Synonyms: Adjective

Argus-eyed, attentive, awake, observant, open-eyed, tenty (also tentie) [Scottish], vigilant, watchful, wide-awake

Synonyms: Noun

admonishment, admonition, alarm (also alarum), caution, forewarning, heads-up, notice, warning

Synonyms: Verb

advise, caution, forewarn, wake, warn

Antonyms: Adjective


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Choose the Right Synonym for alert


watchful, vigilant, wide-awake, alert mean being on the lookout especially for danger or opportunity. watchful is the least explicit term. the watchful eye of the department supervisor vigilant suggests intense, unremitting, wary watchfulness. eternally vigilant in the safeguarding of democracy wide-awake applies to watchfulness for opportunities and developments more often than dangers. wide-awake companies latched onto the new technology alert stresses readiness or promptness in meeting danger or in seizing opportunity. alert traders anticipated the stock market's slide

intelligent, clever, alert, quick-witted mean mentally keen or quick. intelligent stresses success in coping with new situations and solving problems. an intelligent person could assemble it fast clever implies native ability or aptness and sometimes suggests a lack of more substantial qualities. clever with words alert stresses quickness in perceiving and understanding. alert to new technology quick-witted implies promptness in finding answers in debate or in devising expedients in moments of danger or challenge. no match for his quick-witted opponent

Examples of alert in a Sentence


An alert guard stopped the robbers. He was tired and had trouble staying alert while he was driving. She wasn't mentally alert enough to answer the questions. An alert watchdog guarded the door.


They sounded an alert when enemy planes were approaching the city. Medical officials have put out an alert to hospitals to look out for the virus. The government has issued a terrorism alert.


Several neighbors alerted the authorities when they noticed strangers acting suspiciously. The governor alerted island residents that a hurricane was coming. The teacher alerted the students that tests would be given the next day.
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Recent Examples on the Web: Adjective

Be alert for children who might dart across the street or between vehicles on their way to school. Peter Dawson, Houston Chronicle, "Slow down: Tips for school zones in Houston-area, as teachers, parents, kids return to class," 12 Aug. 2019 Managers and investors need to be alert, especially given the growing number of firms with high debts that rely on bulging profits to stay afloat. The Economist, "After years of plenty America Inc is struggling to crank out more earnings," 18 July 2019 Officials in San Mateo, Calif., are reminding residents to be alert after home surveillance video captured a mountain lion prowling the neighborhood on Sunday. Fox News, "Mountain lion spotted prowling California neighborhood prompts warning," 10 July 2019 Stay alert and watch for construction signs and construction workers in the work zone., "Portland metro Tuesday traffic: Expect night paving delays on U.S. 20 near the Santiam Pass," 30 July 2019 Experts and politicians have warned residents to stay alert; the storm is slow-moving and will continue to release rain, increasing flooding risks throughout the affected area. Gabriela Resto-montero, Vox, "Tropical Storm Barry: What we know," 14 July 2019 Guzzle some early and stay alert through those killer opening acts. Blake Ryan, Billboard, "A Guide to Summer Music Festival Season 2019," 24 June 2019 Stay alert on Thursday when your entertainment planet, the Sun, sextiles mischievous Uranus. Venus Australis,, "Your Horoscope This Week," 23 June 2019 Stay alert for sudden changes and know when to dodge and when to jump. Phil Blair, San Diego Union-Tribune, "Rugby’s gung-ho spirit brings out the best in players’ post-career plans," 17 June 2019

Recent Examples on the Web: Noun

The weather service also issued an ozone alert until 4 p.m. Sunday for parts of Colorado, including Denver, calling for limited driving. Saja Hindi, The Denver Post, "Denver weather: 90-plus degree temperatures, thunderstorms, lightning, gusty winds and hail," 4 Aug. 2019 The company's system, which applies the brakes or sends out an alert to warn a driver when a vulnerable road user is crossing the street, certainly could be the difference between an uneventful day and a horrible day for all involved. Eric D. Lawrence, Detroit Free Press, "VW says system can detect pedestrians as long as car isn't going too fast," 3 Aug. 2019 The woman reported the assault to police, who issued an investigative alert with probable cause to arrest Bass. Megan Crepeau,, "Court decision rebuffs common tool used by Chicago police in many arrests for shootings," 30 July 2019 Eddie Jones, principal of Florien High School (a school in one of the three affected districts), told KSLA News that his technology supervisor received an alert on his phone at 4am Sunday about unusually high bandwidth usage. Jim Salter, Ars Technica, "Louisiana declares state of emergency in response to ransomware attack," 26 July 2019 The deputy then became aware of an alert from the Baltimore Police Department that warned of him and Barriere stealing items from lockers after obtaining day passes to upscale gyms, according to the statement. Catalina Righter,, "Gwynn Oak woman charged with stealing credit card in Sykesville gym, charging more than $2,000," 25 July 2019 Newton and her boyfriend had just returned to her house in Brookhaven, MS, after an alert from the home security system that someone had broken in. Tiffany Diane Tso,, "Ally Kostial Was 1 Of 5 Women Killed In Mississippi In 24 Hours," 25 July 2019 Like Paradise, 2,506 others are in areas that can send alerts but have never used the system., "Of small communities across 11 states, more than 500 have a higher wildfire hazard potential than Paradise, Calif.," 23 July 2019 Phillips, who had a multiple-entry business visa to get into Mexico, was stopped at the Guadalajara airport while traveling with her family because of an alert placed on her passport by the U.S. Gustavo Solis, San Diego Union-Tribune, "Federal government sued over surveillance program," 23 July 2019

Recent Examples on the Web: Verb

She and her staff instructed subordinates to alert the front office if Miller called them out of the blue to request statistics or discuss a policy proposal, insisting that the secretary's office would handle the response. al, "How Stephen Miller controls Trump’s immigration policy," 18 Aug. 2019 She and her staff instructed subordinates to alert the front office if Miller called them out of the blue to request statistics or discuss a policy proposal, insisting that the secretary's office would handle the response. Author: Nick Miroff, Josh Dawsey, Anchorage Daily News, "Stephen Miller has singular control of Trump’s immigration policy," 17 Aug. 2019 The initiative, planned to fully launch in early 2020, is designed to alert captains to slow their ships down. Los Angeles Times, "In the Santa Barbara Channel, an underwater sound system tries to keep whales and ships apart," 16 Aug. 2019 The systems are able to alert police almost immediately when a gun is fired in a covered area and identify the type of weapon used, said Fourth District police Commander Brandon Kutz. Robert Higgs,, "Cleveland considers shot sensor technology to help police pinpoint location of gunfire," 14 Aug. 2019 Others remembered specific incidents that alarmed them enough to alert parents, school officials, and the police. Paige Williams, The New Yorker, "Leading Dayton, Ohio, in an Era of Guns, Trump, and Madness," 12 Aug. 2019 Fortunately, tech can learn from another industry that knows how to alert consumers about the dangers of improperly storing and leaking toxic products: the chemical industry. Stephen Nowicki, WIRED, "Big Tech Needs to Use Hazardous Materials Warnings," 10 Aug. 2019 Use Colorado’s new red-flag law to alert law enforcement about anyone who is in distress and has a gun. Dp Opinion, The Denver Post, "Letters: Responding to these tragic shootings; more letters (8/6/19)," 6 Aug. 2019 Millions of people signed up to be alerted when the card was ready for prime time. Wired, "The Apple Card Is Now Available, Just Probably Not for You," 6 Aug. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'alert.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of alert


1618, in the meaning defined at sense 1a


1801, in the meaning defined at sense 1


circa 1868, in the meaning defined at sense 1

History and Etymology for alert

Adjective, Noun, and Verb

Italian all'erta, on the watch, literally, on the height

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Dictionary Entries near alert

Aleppo stone







Statistics for alert

Last Updated

20 Aug 2019

Look-up Popularity

Time Traveler for alert

The first known use of alert was in 1618

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More Definitions for alert



English Language Learners Definition of alert

 (Entry 1 of 3)

: able to think clearly and to notice things



English Language Learners Definition of alert (Entry 2 of 3)

: something (such as a message or loud sound) that tells people there is some danger or problem : an alarm or signal of danger
: the state of being ready for something you have been warned about (such as an attack)



English Language Learners Definition of alert (Entry 3 of 3)

: to give (someone) important information about a possible problem, danger, etc. : to warn (someone)
: to make (someone) aware of something


\ ə-ˈlərt How to pronounce alert (audio) \

Kids Definition of alert

 (Entry 1 of 3)

1 : watchful and ready especially to meet danger But he was alert at night, too, on the road, always listening intently …— Lois Lowry, The Giver
2 : quick to understand and act An alert reader noticed the error in grammar.

Other Words from alert

alertly adverb The prairie dog sat alertly beside the opening of its burrow.



Kids Definition of alert (Entry 2 of 3)

1 : an alarm or signal of danger The police issued an alert.
2 : the period during which an alert is in effect We stayed indoors during the alert.
on the alert
: watchful against danger … the remark had set us all on the alert, straining ears and eyes …— Robert Louis Stevenson, Treasure Island


alerted; alerting

Kids Definition of alert (Entry 3 of 3)

: to make aware of a need to get ready or take action : warn The siren alerted us that a tornado was approaching.

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More from Merriam-Webster on alert

Rhyming Dictionary: Words that rhyme with alert

Thesaurus: All synonyms and antonyms for alert

Spanish Central: Translation of alert

Nglish: Translation of alert for Spanish Speakers

Britannica English: Translation of alert for Arabic Speakers

Comments on alert

What made you want to look up alert? Please tell us where you read or heard it (including the quote, if possible).


a usually brief trip or an expedition

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