Definition of "sentry" in English

noun

1. A guard, particularly on duty at the entrance to a military base.

2. (uncountable) Sentry duty; time spent being a sentry.

3. (nautical) A form of drag to be towed underwater, which on striking bottom is upset and rises to the surface.

4. A watchtower.

5. An animal like a marmot tasked with alerting the pack to danger.