Alert! Alert! Alert! Did I get your attention? When you are alert, you are awake and ready. When you issue an alert you give warning, alerting people to, or notifying them of, a concern.

Alert is one of the rare words that can be used in the same form as a noun, verb, and adjective. In all parts of speech, alert implies preparedness. The word is derived from the French a l'erte which translates to "on the watch." When you hear the word, imagine an alarm going off. The alarm is the alert. When you hear it, you have been alerted and you are now alert.

Primary Meanings of alert

warn or arouse to a sense of danger or call to a state of preparedness
condition of heightened watchfulness or preparation for action
mentally perceptive and responsive;"an alert mind"
Full Definitions of alert

v warn or arouse to a sense of danger or call to a state of preparedness

“We alerted the new neighbors to the high rate of burglaries”
make aware of
Type of:
notify of danger, potential harm, or risk

n condition of heightened watchfulness or preparation for action

“bombers were put on alert during the crisis”
qui vive
air alert
the condition in which combat aircraft are airborne and ready for an operation
red alert
the highest level of alert when an attack by the enemy seems imminent (or more generally a state of alert resulting from imminent danger)
strip alert
a state of readiness for domestic defense aircraft
Type of:
preparation, preparedness, readiness
the state of having been made ready or prepared for use or action (especially military action)

n an automatic signal (usually a sound) warning of danger

alarm, alarum, warning signal
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a small explosive device that is placed on a railroad track and fires when a train runs over it; the sound of the explosion warns the engineer of danger ahead
air alert
the warning signal that begins a period of preparation for an enemy air attack
burglar alarm
a loud warning signal produced by a burglar alarm
fire alarm
a shout or bell to warn that fire has broken out
foghorn, fogsignal
a loud low warning signal that can be heard by fogbound ships
a noise made by the driver of an automobile to give warning;
red flag
a flag that serves as a warning signal
a warning signal that is a loud wailing sound
alarm bell, tocsin
the sound of an alarm (usually a bell)
Type of:
sign, signal, signaling
any nonverbal action or gesture that encodes a message

n a warning that serves to make you more alert to danger

Emergency Alert System
a federal warning system that is activated by FEMA; enables the President to take over the United States airwaves to warn the whole country of major catastrophic events
Type of:
a message informing of danger

adj mentally perceptive and responsive;"an alert mind"

alert to the problems”
alive, awake
aware, cognisant, cognizant
(sometimes followed by `of') having or showing knowledge or understanding or realization or perception

adj engaged in or accustomed to close observation

“caught by a couple of alert cops”
alert enough to spot the opportunity when it came”
“constantly alert and vigilant, like a sentinel on duty”
argus-eyed, open-eyed, vigilant, wakeful
carefully observant or attentive; on the lookout for possible danger
(British informal) not to be deceived or hoodwinked
heads-up, wide-awake
fully alert and watchful
lidless, sleepless
always watchful
marked by keen caution and watchful prudence
not in a state of sleep; completely conscious
full of life and energy
unalert, unvigilant, unwatchful
not alert to what is potentially dangerous
not alert to danger or deception
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adj quick and energetic

brisk, lively, merry, rattling, snappy, spanking, zippy
possessing or exerting or displaying energy

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