sentinel
Americannoun
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sentinels
plural
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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)
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sentinels,
present (3rd person singular)
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sentineled,
past participle, past
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sentinelled,
past participle, past (especially British)
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sentineling,
present participle
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sentinelling
present participle (especially British)
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
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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:
Profiling sentinel antibodies might eventually support vaccine research, vaccine development and medical care for people who are especially vulnerable to weak immune responses.
From Science Daily ● Aug. 21, 2026
I wanted to ask him if he’d sign this book, which had now begun to write its own mythology as it sat sentinel over his other signed books on the shelf behind me.
From Los Angeles Times ● Jan. 8, 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
Then they went on through the Citadel gate, where the sentinel stared at them in wonder and dismay as they passed by.
From "The Return of the King" by J.R.R. Tolkien
“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
All of Orange County Fire Watch’s sentinels started as volunteers with the county parks or the Irvine Ranch Conservancy, which boast pools of 1,200 and 500 volunteers, respectively.
From Los Angeles Times ● Aug. 15, 2025
"We always say these animals are sentinels because they feel first what's going to come to us. It's happening to them, it's going to happen to us."
From BBC ● Dec. 25, 2023
They made indifferent sentinels, for in many places their ranks had been broken by the rhubarb plant, and they lay with crumpled heads and listless stems, making a pathway for the rabbits.
From "Rebecca" by Daphne du Maurier
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
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 John Algernon Owens
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 A. D. T. (Adeline Dutton Train) Whitney
At another point, emerging from a maze of mountains, the locomotive shoots into a plain, forty or fifty miles square, and sentineled on every side by savage peaks.
From John L. Stoddard's Lectures, Vol. 10 (of 10) Southern California; Grand Canon of the Colorado River; Yellowstone National Park by John L. (John Lawson) Stoddard
And then as if commanded by a voice, his eyes turned to the dead cottonwood stub which had sentineled the little oasis of trees for many years.
From The Alaskan by James Oliver Curwood
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 Stephen Crane
Here and there, these openings are sentinelled, as it were, by little fairy islets, green as emerald, and waving with palms.
From Omoo by Herman Melville
Across the snow-fields shimmered a translucent rosy glow, so that they seemed no longer bleak and desolate, but lay spread like an unfurled banner of glory betwixt the great peaks which sentinelled them round.
From The Vision of Desire by Margaret Pedler
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 E. M. Ashe
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 John Trotwood Moore
Dignity and grace lie in these tall swaying trees sentinelling the way on either side.
From In the Claws of the German Eagle by Albert Rhys Williams
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 Theodore Dreiser
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