Sentry is a noun that refers to a guard to control access to a place.

The origin of our word of the day is the French word sentinelle (cent uh NELL). Its shortened version, sentry, entered English in the 17th century. Here’s an example:

Mike’s trophy was so valuable, he felt a sentry was needed around it at all times. It didn’t have the heart to tell him there was no need to guard a trophy for office champ in the annual darts competition.