Pronunciation: (u-lûrt'),[key] —adj. 1. fully aware and attentive; wide-awake; keen: an alert mind. 2. swift; agile; nimble.
—n. 1. an attitude of vigilance, readiness, or caution, as before an expected attack.
2. a warning or alarm of an impending military attack, a storm, etc.: We'd just boarded the bus when the alert sounded. 3. the period during which such a warning or alarm is in effect.
4. on the alert, on guard against danger; in readiness; vigilant: The state police are on the alert for an escaped convict believed to be in the area.
—v.t. 1. to warn (troops, ships, etc.) to prepare for action.
2. to warn of an impending raid, attack, storm, etc.: The radio alerted coastal residents to prepare for the hurricane. 3. to advise or warn; cause to be on guard: to alert gardeners to the dangers of some pesticides.