Etymology First attested in the 1570s from Middle French sentinelle (“watch or guard kept by a soldier”), from Old Italian sentinella, probably from sentina + -ella, from sentire (“perceive, watch, hear”), from sentiō (“feel, perceive by the senses”). See also sense, sentient.
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A sentry, watch, or guard.
They promised faithfully to bear their confinement with patience, and were very thankful that they had such good usage as to have provisions and light left them; for Friday gave them candles (such as we made ourselves) for their comfort; and they did not know but that he stood sentinel over them at the entrance.1719 May 6 (Gregorian calendar), [Daniel Defoe], The Life and Strange Surprizing Adventures of Robinson Crusoe, […], London: […] W[illiam] Taylor […], →OCLC:
the sentinels who paced the ramparts1849–1861, Thomas Babington Macaulay, chapter XII, in The History of England from the Accession of James the Second, volume (please specify |volume=I to V), London: Longman, Brown, Green, and Longmans, →OCLC:
1 more example
that princes do keep due sentinel1625, Francis [Bacon], “Of Empire”, in The Essayes […], 3rd edition, London: […] Iohn Haviland for Hanna Barret, →OCLC:
“I will not permit the poorest centinel to be treated with injustice.”1789, John Moore, Zeluco, Valancourt, published 2008, page 33:
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Computer, Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Science, Sciences A unique value recognised by a computer program for processing in a special way, or marking the end of a set of data.
The <xmp> tag is a sentinel that suspends web-page processing and displays the subsequent text literally
[…] a sentinel value that indicates a missing entry.2016, Jake VanderPlas, Python Data Science Handbook, page 120:
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A sentinel crab.
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Epidemiology, Medicine, Sciences A sign of a health risk (e.g. a disease, an adverse effect).
sentinel animals can be used to explore endemic diseases.
Etymology First attested in the 1570s from Middle French sentinelle (“watch or guard kept by a soldier”), from Old Italian sentinella, probably from sentina + -ella, from sentire (“perceive, watch, hear”), from sentiō (“feel, perceive by the senses”). See also sense, sentient.
1
To watch over as a guard.
He sentineled the north wall.
2
To post a guard for.
He sentineled the north wall with just one man.
The old-fashioned stoop, with its suggestive benches on either side, lay solitary and silent in the moonlight; the garden path, weedily overgrown since father's death, and sentineled here and there with ragged hollyhock, lay quiet and dew-laden […]1873, Harper's New Monthly Magazine, volume 46, page 562: