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Definitions

on the alert

ADJECTIVE
unsleeping
Synonyms
WEAK
alive astir attentive awake careful heedful insomniac insomnious observant on guard on the lookout on the qui vive sleepless vigilant waking wary watchful wide-awake
ADJECTIVE
wakeful
Synonyms
WEAK
alive astir attentive careful heedful insomniac insomnious observant on guard on the lookout on the qui vive sleepless unsleeping vigilant waking wary watchful wide-awake
Antonyms
WEAK
sleepy unaware

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

The league is on the alert regarding head injuries, but nobody is sure why there are more concussions this season than previously.

From Los Angeles Times • Jun. 15, 2026

In response to the floods, the worst in 30 years, authorities were on the alert, reinforcing earthen barriers and preparing to evacuate if needed.

From Barron's • Jun. 2, 2026

Also be on the alert for any signs your financial adviser is sure we’re in—or not in—a bubble.

From The Wall Street Journal • May 8, 2026

For now, forecasters warned the Leeward Islands, where the Caribbean and Atlantic join, to be on the alert.

From BBC • Sep. 6, 2023

She pressed the bell button three times before she entered the hallway so that Mama could be on the alert and make sure that Francie wouldn’t be attacked by someone lurking in the hallways.

From "A Tree Grows in Brooklyn" by Betty Smith

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