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:
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
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
Beal noted one of the sentinel signs that a farm has been infected is dead barn cats that have drunk the infected, raw milk.
From Los Angeles Times ● Oct. 4, 2024
Two sentinel boulders, dripping wet, decorated with flowers, ferns, moss, weeds—everything that loved water—guarded a bathtub-sized spring.
From "My Side of the Mountain" by Jean Craighead George
The birds feed on insects living on rhinos and can also act as sentinels - calling to warn their hosts when danger approaches.
From BBC ● Aug. 25, 2026
“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
While the latter two were essentially vaporized by the fire, the burned shells of the others remain, steel sentinels left ravaged by the flames.
From Los Angeles Times ● Apr. 15, 2025
Or sentinels, keeping guard, waiting patiently and silently.
From "Nine, Ten: A September 11 Story" by Nora Raleigh Baskin
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
Eight Corinthian pillars sentineled it, resting on a marble base which seemed to spring up out of the flag-stones themselves, and towering to the projecting entablature above.
From The Bishop of Cottontown A Story of the Southern Cotton Mills by John Trotwood Moore
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
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
The tent was sentinelled, and Dujardin was alone with the past.
From White Lies by Charles Reade
Under what a tempest of conjectures she looked down and across the great hall to the closed and sentinelled door of that front drawing-room so rife with poignant recollections.
From Kincaid's Battery by Alonzo Kimball
Kendric told Barlow what he had learned during the evening; how the walls were sentinelled and how at the present moment under the same roof with them was an American girl, held for ransom.
From Daughter of the Sun A Tale of Adventure by Jackson Gregory
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 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
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
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.
