sentinel

• centinel (obsolete)

1570s, from Middle French sentinelle, from Old Italian sentinella (perhaps via a notion of "perceive, watch", compare Italian sentire (“to feel, hear, smell”)), from Latin sentiō (“feel, perceive by the senses”). See sense, sentient.

• IPA^(key): /ˈsɛntɪnəl/

• Audio (US):

  (file)

sentinel (plural sentinels)

1. A sentry, watch, or guard.
   • 1719 May 6 (Gregorian calendar), [Daniel Defoe], The Life and Strange Surprizing Adventures of Robinson Crusoe, […], London: […] W[illiam] Taylor […], →OCLC:

     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.

   • 1849–1861, Thomas Babington Macaulay, chapter 12, in The History of England from the Accession of James the Second, volumes (please specify |volume=I to V), London: Longman, Brown, Green, and Longmans, →OCLC:

     the sentinels who paced the ramparts

   • 1625, Francis [Bacon], “Of Empire”, in The Essayes […], 3rd edition, London: […] Iohn Haviland for Hanna Barret, →OCLC:

     that princes do keep due sentinel

2. (obsolete) A private soldier.
   • 1789, John Moore, Zeluco, Valancourt, published 2008, page 33:

     “I will not permit the poorest centinel to be treated with injustice.”

3. (computer science) 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

   • 2016, Jake VanderPlas, Python Data Science Handbook, page 120:

     […] a sentinel value that indicates a missing entry.

4. A sentinel crab.
5. (attributive, medicine, epidemiology) A sign of a health risk (e.g. a disease, an adverse effect).

   sentinel animals can be used to explore endemic diseases.

6. (Can we verify⁽⁺⁾ this sense?) (figuratively) Someone who is hardworking and dutiful.

sentinel (third-person singular simple present sentinels, present participle (US) sentineling or (UK) sentinelling, simple past and past participle (US) sentineled or (UK) sentinelled)

1. (transitive) To watch over as a guard.

   He sentineled the north wall.

2. (transitive) To post a guard for.

   He sentineled the north wall with just one man.

   • 1873, Harper's New Monthly Magazine, volume 46, page 562:

     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 […]

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