sentinel
Americannoun
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a person or thing that watches or stands as if watching.
The cats were the sentinels of the house, patrolling constantly for rodents, dogs, and other invaders.
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a soldier stationed as a guard to challenge all comers and prevent a surprise attack.
Lincoln refused to make his home mansion a garrison during the Civil War, but plain-clothes sentinels did patrol the property
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Digital Technology. tag.
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Medicine/Medical. an indication or mark that a disease is present or prevalent.
New viruses in the wastewater can be used as sentinels of future outbreaks.
verb (used with object)
adjective
noun
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a person, such as a sentry, assigned to keep guard
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computing a character used to indicate the beginning or end of a particular block of information
verb
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to guard as a sentinel
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to post as a sentinel
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to provide with a sentinel
Other Word Forms
Derived Forms
Inflected Forms
Nouns
Participles
Conjugated Forms
Present
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sentinelsimple
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sentinelssimple
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have sentineledperfect
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have sentinelledperfect
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has sentineledperfect
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has sentinelledperfect
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am sentinelingprogressive
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am sentinellingprogressive
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are sentinelingprogressive
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are sentinellingprogressive
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is sentinelingprogressive
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is sentinellingprogressive
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have been sentinelingperfect progressive
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have been sentinellingperfect progressive
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has been sentinelingperfect progressive
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has been sentinellingperfect progressive
Past
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sentineledsimple
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sentinelledsimple
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had sentineledperfect
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had sentinelledperfect
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was sentinelingprogressive
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was sentinellingprogressive
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were sentinelingprogressive
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were sentinellingprogressive
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had been sentinelingperfect progressive
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had been sentinellingperfect progressive
Future
Etymology
Origin of sentinel
First recorded in 1570–80; from Middle French sentinelle, from Italian sentinella, derivative of Old Italian sentina “vigilance,” from Latin sent(īre) “to feel” + -īna -ine 2
Explanation
A sentinel is a guard, a lookout, a person keeping watch. It's often a soldier, but not always. If you're watching a pot, waiting for it to boil, you're standing sentinel over it — and incidentally, it won't boil until you leave. Etymologists think sentinel stems from the Old Italian words sentina, meaning "vigilance," and sentire, "to hear or perceive." It's a close cousin of sentry, which means the same thing. You can use sentinel as a noun or a verb. A kid in a snowball war might be the sentinel, patrolling the entrance to the fort. Wolves stand sentinel over their kill, stepping aside only for the alpha male, who always eats first.
Vocabulary lists containing sentinel
The Vocabulary.com Top 1000
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Unit 1: Telling Details
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Common Senses: Sent, Sens ("Feel")
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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.
See Examples For:
The steely husks stood sentinel over unfathomable loss for weeks or months until they were towed away and sold as scrap.
From Los Angeles Times ● Jan. 26, 2026
The mean rescue sentinel did not think so.
From Salon ● Dec. 6, 2024
The church stood empty like a silent sentinel over a small cemetery next to it.
From Slate ● Oct. 24, 2024
Intriguingly, the system being attacked normally works as a sentinel or guard, whose job it is to detect invading viruses.
From Science Daily ● May 23, 2024
The best way to find a virus in the wild, at the present time, is to place a sentinel animal at the suspected location of the virus and hope the animal gets sick.
From "The Hot Zone" by Richard Preston
“We stand on the walls, sentinels of the inner sanctum, against the assault of AI slop. The Ontology is based firmly in reality—there is, here, a dialectic between ground truth, tribal knowledge, and enhancements.”
From The Wall Street Journal ● May 5, 2026
“We stand on the walls, sentinels of the inner sanctum, against the assault of AI slop,” Karp said in his letter to shareholders.
From Barron's ● May 4, 2026
Dogs get more tick bites and are tested more often for vector-borne diseases than people, so they can be sentinels for their owners.
From Los Angeles Times ● Aug. 18, 2025
"Our dogs could be our sentinels -- the canine in the proverbial coal mine."
From Science Daily ● Jan. 18, 2024
The three cards stand like little sentinels, waiting.
From "X: A Novel" by Ilyasah Shabazz
As by the elms that line its street, the hills that watch its roofs, Lyme, Conn., is sentineled by artistic good usage, fortressed by aesthetic tradition.
From Time Magazine Archive
He jumped off, hitched Red Squirrel to one of the posts that sentineled the curbstone, and passed quietly round into the "shady turn."
From The Other Girls by Whitney, A. D. T. (Adeline Dutton Train)
A fort, mounting eight guns, sentineled the approach to the city from beneath, while the heights above were guarded by a three-banked battery.
From Sword and Pen Ventures and Adventures of Willard Glazier by Owens, John Algernon
It was far back from the street and was sentineled on either side by an uncompromising fir tree.
From The Heart's Country by Vorse, Mary Heaton
How the Southern Portal of the Highlands stands sentineled by Stony Point, a humble crag converted by the courage of Anthony Wayne into a mountain peak of Liberty.
From The Hudson Three Centuries of History, Romance and Invention by Bruce, Wallace
He was stationed at Fort Knox, where he sentinelled the country’s gold reserves.
From The New Yorker ● Mar. 27, 2017
Williamstown, sentinelled with maple trees, smiles at the Berkshires.
From Time Magazine Archive
At the foot of the hill, where two lines of maples sentinelled the way, an electric lamp glowed high among the embowering branches, and made most wonderful shadow-etchings on the road below it.
From The Monster and Other Stories by Crane, Stephen
And that no sordidness might pass therein He sentinelled the door with savage jinn, Invisible and with the flaming powers Of Sheol in their guarding scimitars.
From Legends & Romances of Spain by Spence, Lewis
In the Close of Durdlebury, greenswarded, silent, sentinelled by immemorial elms that guard the dignified Gothic dwellings of the cathedral dignitaries, was James Marmaduke Trevor born.
From The Rough Road by Locke, William John
The two great poplar-trees, sentineling what had once been the gate of the old Gordon homestead, had been spared through all the industrial changes.
From The Quickening by Ashe, E. M.
The dry stalks, sentinelling the seared ground, waved their tattered remnants of unpicked bolls to and fro—summer's battle flags which had not yet fallen.
From The Bishop of Cottontown A Story of the Southern Cotton Mills by Moore, John Trotwood
Dignity and grace lie in these tall swaying trees sentinelling the way on either side.
From In the Claws of the German Eagle by Williams, Albert Rhys
The round green hills sentinelling the broad, expansive bosom of the Hudson held her attention by their beauty as the train followed the line of the stream.
From Sister Carrie: a Novel by Dreiser, Theodore
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
