sentry

Definition of Sentry in English :

a person employed to keep watch for some anticipated event

WordNet Lexical Database for English. Princeton University. 2010.

Sentry

noun plural -tries

1.

a soldier who guards or prevents unauthorized access to a place, keeps watch for danger, etc

2.

the watch kept by a sentry

nounWord forms: plural ˈsentries

1.

a sentinel; esp., any of the men of a military guard posted to guard against, and warn of, danger

2. Rare

guard or watch

to keep sentry

n. pl. sen·tries

1. A guard, especially a soldier posted at a given spot to prevent the passage of unauthorized persons.

2. The duty of a sentry; watch.