I. ə-ˈlərt adjective
Etymology: Italian all'erta, on the watch, literally, on the height
Date: 1618
1.
a. : watchful and prompt to meet danger or emergency
b. : quick to perceive and act
2. : active , brisk
Synonyms: see watchful , intelligent
• alert·ly adverb
• alert·ness noun
II. noun
Date: 1803
1. : a state of careful watching and readiness especially for danger or opportunity
on 24-hour alert
2.
a. : an alarm or other signal of danger
b. : an urgent notice
an alert to parents…about new immunization requirements — Ann Schrader
3. : the period during which an alert is in effect
III. transitive verb
Date: circa 1868
1. : to call to a state of readiness : warn
2. : to make aware of
alert ed the public to the dangers of pesticides