Meanings
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1
noun
a guard or watchman posted to keep lookout
A lone sentinel stood at the gate through the night.
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2
noun
a special value in a computer program that marks a boundary, ending, or exceptional condition
The parser used a null byte as a sentinel to mark the end of the string.
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3
noun
a sign or indicator used to warn of a risk, disease, or important change
Public-health teams monitored sentinel cases for evidence of a wider outbreak.
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4
verb
to watch over or guard
The ridge was sentineled by soldiers throughout the storm.
Thesaurus
Etymology
From Middle French sentinelle, from Italian sentinella, probably connected with sentire ("to feel, perceive, hear"), from Latin sentire. The computing sense keeps the idea of a watcher or marker: a value that stands guard at an important boundary.