1
a
: watchful and prompt to meet danger or emergency
an alert guard
trying to stay alert to possible problems
b
: quick to perceive and act
mentally alert
alertly
adverb
alertness
noun
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
traffic alerts
They sounded the alert.
b
: an urgent notice
… an alert to parents … about new immunization requirements.—
Ann Schrader
Ann Schrader3
: the period during which an alert is in effect
alerted; alerting; alerts
1
: to call (someone) to a state of readiness : warn
alerted the school board of a possible teachers' strike
alert the authorities
2
: to make (someone) aware of something
alerted the public to the dangers of pesticides
Examples of alert in a Sentence
Adjective
An alert guard stopped the robbers.
He was tired and had trouble staying alert while he was driving.
She wasn't mentally alert enough to answer the questions.
An alert watchdog guarded the door.
Noun
They sounded an alert when enemy planes were approaching the city.
Medical officials have put out an alert to hospitals to look out for the virus.
The government has issued a terrorism alert.
Verb
Several neighbors alerted the authorities when they noticed strangers acting suspiciously.
The governor alerted island residents that a hurricane was coming.
The teacher alerted the students that tests would be given the next day.
Recent Examples on the Web
Hollie Silverman, MSNBC Newsweek, 21 Oct. 2025
According to Fox 5, the baby was found with her umbilical cord still attached, was wrapped only in a sheet but was alert and conscious.
—Emma Bussey, FOXNews.com, 20 Oct. 2025
Emerson Clarridge, Fort Worth Star-Telegram, 22 Oct. 2025
When temperatures start to drop below 32 degrees, the National Weather Service issues three types of alerts.
—Janet Loehrke, USA Today, 22 Oct. 2025
Anna Skinner, MSNBC Newsweek, 24 Oct. 2025
Identity Theft companies can monitor personal information like your Social Security Number (SSN), phone number and email address, and alert you if it is being sold on the dark web or being used to open an account.
—Kurt Knutsson, FOXNews.com, 24 Oct. 2025
See All Example Sentences for alert
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Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
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Adjective
Residents have been urged to remain alert and follow official guidance during any subsequent seismic activity.
—Hollie Silverman, MSNBC Newsweek, 21 Oct. 2025
According to Fox 5, the baby was found with her umbilical cord still attached, was wrapped only in a sheet but was alert and conscious.
—Emma Bussey, FOXNews.com, 20 Oct. 2025
Noun
Husband arrested [Get our breaking news alerts.
—Emerson Clarridge, Fort Worth Star-Telegram, 22 Oct. 2025
When temperatures start to drop below 32 degrees, the National Weather Service issues three types of alerts.
—Janet Loehrke, USA Today, 22 Oct. 2025
Verb
Significant waves Myriad weather alerts warning of hazardous seas are in place along the Pacific Northwest coast, including a high surf advisory, small craft advisory, and others.
—Anna Skinner, MSNBC Newsweek, 24 Oct. 2025
Identity Theft companies can monitor personal information like your Social Security Number (SSN), phone number and email address, and alert you if it is being sold on the dark web or being used to open an account.
—Kurt Knutsson, FOXNews.com, 24 Oct. 2025
See All Example Sentences for alert
Cite this Entry
“Alert.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/alert. Accessed 29 Oct. 2025.
Copy CitationKids Definition
alert
1 of 3 adjective1
a
: being watchful and ready to meet danger
b
: quick to understand and act
2
alertly
adverb
alertness
noun
alert
2 of 3 noun1
: a signal of danger
2
: the period during which an alert is in effect
alert
3 of 3 verb
: to call to a state of readiness : warn
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