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English definition of “alert”

alert

noun     /əˈlɜːt/
[C] a warning about a possibly dangerous situation: a bomb alert Threats and warningsEmergency services in general
be on full/red alert to be expecting problems and ready to deal with them: Police in the region were on full alert against further attacks.Threats and warningsEmergency services in general
(Definition of alert noun from the Cambridge Learner's Dictionary © Cambridge University Press)

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