Definition of alert in English:

Share this entry


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.
vigilant, watchful, attentive, observant, wide awake, circumspect;
on the lookout, on one's guard, on one's toes, on the qui vive
informal heads-up, keeping one's eyes open/peeled, bright-eyed and bushy-tailed
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


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.
vigilance, watchfulness, attentiveness, alertness, circumspection
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.


[with object]
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


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.



Pronunciation: /əˈlərtlē/
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

Syllabification: a·lert

Share this entry

What do you find interesting about this word or phrase?

Comments that don't adhere to our Community Guidelines may be moderated or removed.