SENTRY
lookout, lookout man, sentinel, sentry, watch, spotter, scout, picket
(noun) a person employed to keep watch for some anticipated event
Source: WordNet® 3.1
Etymology
Noun
sentry (plural sentries)
A guard, particularly on duty at the entrance to a military base.
(uncountable) Sentry duty; time spent being a sentry.
(nautical) A form of drag to be towed underwater, which on striking bottom is upset and rises to the surface.
A watchtower.
Synonyms
• (nautical drag): kite
Anagrams
• Tyners
Source: Wiktionary
Sen"try, n.; pl. Sentires. Etym: [Probably from OF. senteret a little
patch; cf. F. sentier path, and OF. sente. See Sentinel.]
1. (Mil.)
Definition: 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.
Sentry box, a small house or box to cover a sentinel at his post, and
shelter him from the weather.
Source: Webster’s Unabridged Dictionary 1913 Edition