Definition of alert in English:

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Pronunciation: /əˈləːt/


1Quick to notice any unusual and potentially dangerous or difficult circumstances; vigilant: an alert police officer discovered a lorry full of explosive schools need to be constantly alert to this problem
More example sentences
  • At the other end Dermot Byrne almost got clear but Farrell Cuddihy was very alert to clear the danger.
  • There are signs that Congress is at least somewhat alert to these dangers.
  • Though at times they don't seem to be the most aware of animals, sheep are very alert to mood swings, and this time was no exception.
vigilant, wide awake, aware, watchful, attentive, observant, circumspect, wary, chary, heedful, canny;
on the lookout, on one's guard, on one's toes, all ears, keeping one's eyes open/peeled, keeping a weather eye open, on the qui vive
1.1Able to think clearly; intellectually active: she remained active and alert until well into her eighties
More example sentences
  • Throughout his life he remained very alert and active until very recent times.
  • Tanner was alert and able to answer questions but was not extremely active.
  • Still active and alert Mary attributes her longevity to plenty of hard work, good genes, a healthy lifestyle and a positive outlook on life in general.
quick-witted, sharp, bright, quick, keen, perceptive, wide awake, responsive, agile, acute, astute
informal on the ball, on one's toes, quick off the mark, quick on the uptake, all there, with it, bright-eyed and bushy-tailed


[mass noun]
1The state of being watchful for possible danger: security forces are on the alert for an upsurge in violence
More example sentences
  • The main north-south highway was reopened on Thursday but motorists were urged to remain on alert against possible dangers caused by the continuing heavy rains.
  • And now, as his execution by lethal injection nears, some clinics providing abortions are on alert for possible violence.
  • But the industry was put on alert about the possible tax rises at a conference this month when a representative from the Revenue said the memoranda would need to be reviewed.
vigilance, watchfulness, carefulness, attentiveness, guardedness, care, caution, cautiousness, wariness, chariness, alertness, circumspection, prudence, heedfulness, heed, mindfulness
1.1 [count noun] An announcement or signal warning of danger: a bomb alert
More example sentences
  • A flood alert was sounded in Kinnaur, Shimla, Kulu and Mandi districts last evening after water started overflowing from the lake, bringing along a lot of silt.
  • The all-clear had in fact sounded from an initial alert when the bomb was dropped.
  • The Environment Agency issued flood alerts for several rivers and part of the A12 was sealed off.
warning, caution, notification, notice, exhortation, injunction;
siren, alarm, signal, danger signal, distress signal
1.2 [count noun] A period of vigilance following a warning of danger: traffic was halted during the alert
More example sentences
  • The country is on a war alert following terrorist attacks on its Parliament building.
  • The incident follows a similar alert at a post office earlier this week.
  • Thousands of holidaymakers who lost luggage following the airport security alert earlier this month are unlikely to be able to claim compensation from their insurers, it emerged last week.
1.3 [count noun] A signal on an electronic device that prompts the user to do something or attracts their attention: a vibrating alert is a discreet alternative to ringtones
More example sentences
  • It took a little getting used to, but after a while, I realised I was back in Singapore, where it doesn't matter if phones ring or SMS alerts beep loudly on the trains.
  • For example, certain software programs allow users to send e-mail alerts.
  • This software can now, for example, send out a real-time alert to Outlook users when it picks up on an appointment conflict.


[with object]
Warn (someone) of a danger or problem: he alerted people to the dangers of smoking police were alerted after three men drove away without paying
More example sentences
  • Wenger did the game a service by alerting us to the dangers.
  • Surely it would make more sense to put up an advert outside a football ground alerting men to the dangers of testicular or prostate cancer?
  • A pensioner is lucky to be alive after her dog alerted her to the danger of a fire at her home
warn, notify, apprise, caution, put on one's guard, forewarn, put on the qui vive, arouse
informal tip off, clue in, put in the picture, put wise



Pronunciation: /əˈləːtli/
Example sentences
  • Both Aaron and Ryan moved carefully and alertly, and Ryan had his sword drawn.
  • An original thinker always alertly attuned to contemporary culture, he was admired for his intellectual style and the felicity with which he expressed his ideas in his many books and articles.
  • Thankfully, however, the deer do wise up quickly, alertly scanning their surroundings for different sounds or a hint of movement that wasn't there the day before.


Late 16th century (originally in military use): from French alerte, from Italian all' erta 'to the watchtower'.

  • This comes from the Italian military phrase all' erta, ‘on the lookout’ or, more literally, ‘to the watchtower’. It was originally a military term in English too, before it acquired its more general meaning. Alert was first used as an adverb, so you could say that the later expression on the alert strictly means ‘on the on the lookout’.

Words that rhyme with alert

advert, animadvert, assert, avert, Bert, blurt, Burt, cert, chert, concert, controvert, convert, curt, desert, dessert, dirt, divert, exert, flirt, girt, hurt, inert, insert, introvert, Kurt, malapert, overt, pert, quirt, shirt, skirt, spirt, spurt, squirt, Sturt, subvert, vert, wort, yurt

For editors and proofreaders

Line breaks: alert

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