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
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:
"When you only have a handful of species that can persist in environments like that, and they're really sensitive to change, those serve as really good sentinel taxa," Adams said.
From Science Daily ● Jan. 10, 2026
Ahead of our return to the city, we drive back up the ridge, back through Burguete, the inn still shuttered, and up to Roncesvalles, where the old monastery looms like a sentinel over the pass.
From Salon ● Nov. 8, 2025
The church stood empty like a silent sentinel over a small cemetery next to it.
From Slate ● Oct. 24, 2024
But sentinel landscapes are prioritized for funding through certain grants, he said.
From Los Angeles Times ● May 23, 2024
But he was not sorry to be a trusted sentinel for them.
From "The Once and Future King" by T. H. White
“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
A few rise above head-height, the most energetic sentinels of regeneration.
From Los Angeles Times ● Mar. 13, 2026
"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
The valley of the rock-laser sentinels lay far below.
From "Tristan Strong Punches a Hole in the Sky" by Kwame Mbalia
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
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
Poor lad! he was coming down the pass last night, not knowing that it was sentineled by the enemy.
From Then Marched the Brave by Anna S. Hicks
It is nature's grand police, vigilant and faithful, sentineled in the soul, guarding against violence to peace and life.
From John Brown An Address at the 14th Anniversary of Storer College by Frederick Douglass
It was far back from the street and was sentineled on either side by an uncompromising fir tree.
From The Heart's Country by Mary Heaton Vorse
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
The tent was sentinelled, and Dujardin was alone with the past.
From White Lies by Charles Reade
One side was sentinelled by sun-flowers and another side by transplanted laurel and rhododendron shrubs, and hidden in the plant-and-flower-bordered squares were the vegetables that won her step-mother's tolerance of Hale's plan.
From The Trail of the Lonesome Pine by John Fox
The park-gates were shut up, locked, sentinelled: the place could not be entered.
From Villette by Charlotte Brontë
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
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.
