A guard or sentinel posted to keep watch.

A soldier stationed to keep guard at a specific place.

सैनिक

English Usage: The sentry changed shifts every four hours to maintain vigilance.

Hindi Usage: चौकीदार हर चार घंटे में शिफ्ट बदलता था ताकि सतर्कता बनी रहे।

To act as a guard or watch.

पहरा देना

English Usage: He was sentried in the old fortress throughout the night.

Hindi Usage: उसे पुरानी किले में सारी रात पहरा दिया गया।