Definition of alert noun from the Oxford Advanced American Dictionary

     

    alert

     noun
    noun
    NAmE//əˈlərt//
     
     
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  1. 1 [singular, uncountable] a situation in which people are watching for danger and are ready to deal with it Police are warning the public to be on the alert for suspicious packages. More than 5,000 troops have been placed on (full) alert.
  2. 2 [countable] a warning of danger or of a problem see also red alert
See the Oxford Advanced Learner's Dictionary entry: alert