Webster's Revised Unabridged Dictionary · 1913

Sentry

Sentry , noun

[Probably from Old French senteret a little patch; compare French sentier path, and Old French sente. See Sentinel.]

1.
(Military) A soldier placed on guard; a sentinel.
2.
Guard; watch, as by a sentinel.
Here toils, and death, and death's half-brother, sleep, Forms terrible to view, their sentry keep. — Dryden
Collocations (1)
Sentry box , a small house or box to cover a sentinel at his post, and shelter him from the weather.