Definition of alert in English:


Syllabification: a·lert
Pronunciation: /əˈlərt


1Quick to notice any unusual and potentially dangerous or difficult circumstances; vigilant: an alert police officer discovered a truck full of explosives 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.
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, on one's toes
informal on the ball, quick on the uptake, all there, with it


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1The state of being watchful for possible danger: security forces were placed on alert
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.
1.1An announcement or signal warning of danger: a bomb alert an alert sounded and all the fighters took off
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, notification, notice;
siren, alarm, signal, danger signal, distress signal
1.2A period of vigilance in response to 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.


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Warn (someone) of a danger, threat, or problem, typically with the intention of having it avoided or dealt with: 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, forewarn, put on one's guard, put on the qui vive
informal tip off, clue in


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


on the alert

Vigilant and prepared: the security forces must be on the alert for an upsurge in violence
More example sentences
  • The terrorist decides where and when he will strike, while the security forces must constantly be on the alert.
  • The committee appeals to everyone to exercise more vigilance and to be on the alert at all times, particularly in the run-up to Christmas.
  • To avoid overlooking opportunities, we must forever be on the alert.



More 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.

Definition of alert in:

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