sentinel

[sen-tn-l] /ˈsɛn tn l/
noun
1.
a person or thing that watches or stands as if watching.
2.
a soldier stationed as a guard to challenge all comers and prevent a surprise attack:
to stand sentinel.
3.
Digital Technology, tag1 (def 9a).
verb (used with object), sentineled, sentineling or (especially British) sentinelled, sentinelling.
4.
to watch over or guard as a sentinel.
Origin
1570-80; < Middle French sentinelle < Italian sentinella, derivative of Old Italian sentina vigilance (Latin sent(īre) to observe) + -īna -ine2)
Related forms
sentinellike, adjective
sentinelship, noun
unsentineled, adjective
unsentinelled, adjective
Synonyms
1, 2. sentry, guard, watch, lookout.
Examples from the web for sentinel
  • Another phrase used to describe this is a sentinel headache.
British Dictionary definitions for sentinel

sentinel

/ˈsɛntɪnəl/
noun
1.
a person, such as a sentry, assigned to keep guard
2.
(computing) a character used to indicate the beginning or end of a particular block of information
verb (transitive) -nels, -nelling, -nelled
3.
to guard as a sentinel
4.
to post as a sentinel
5.
to provide with a sentinel
Word Origin
C16: from Old French sentinelle, from Old Italian sentinella, from sentina watchfulness, from sentire to notice, from Latin
Word Origin and History for sentinel
n.

1570s, from Middle French sentinelle (16c.), from Italian sentinella "a sentinel." OED says "No convincing etymology of the It. word has been proposed," but perhaps (via a notion of "perceive, watch"), from sentire "to hear," from Latin sentire "feel, perceive by the senses" (see sense (n.)).