Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English

English definition of “alert”

See all translations

alert

adjective uk   /əˈlɜːt/ us    /-ˈlɝːt/
C1 quick to see, understand, and act in a particular situation: I'm not feeling very alert today - not enough sleep last night! A couple of alert readers posted comments on the website pointing out the mistake. Parents should be alert to sudden changes in children's behaviour.
More examples
alertness
noun [U] uk   /-nəs/ us  

alert

noun [C or U] uk   /əˈlɜːt/ us    /-ˈlɝːt/
C1 a warning to people to be prepared to deal with something dangerous: a bomb alert The army was put on (full) alert as the peace talks began to fail. The public were warned to be on the alert for (= watching carefully for) suspicious packages.

alert

verb [T] uk   /əˈlɜːt/ us    /-ˈlɝːt/
C2 to warn someone of a possibly dangerous situation: An anonymous letter alerted police to the possibility of a terrorist attack at the airport.
More examples
(Definition of alert from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
What is the pronunciation of alert?
Add Cambridge dictionaries to your browser to your website

More meanings of “alert”

Definitions of “alert” in other dictionaries

Word of the Day

glacial

made or left by a glacier

Word of the Day

Let’s celebrate! (words and phrases for parties)

by Kate Woodford,
December 17, 2014
​​​ With Christmas and New Year almost upon us, we thought it a good time to look at the language of parties and celebrations. First, let’s start with the word ‘party’ itself. To have or throw a party or, less commonly, to give a party is to arrange a party: We’re having a

Read More 

cinderella surgery noun

December 15, 2014
cosmetic surgery to the feet We have all heard of people having nose jobs, boob jobs and liposuction – but now a new trend growing in popularity in America: Cinderella surgery.

Read More