lookout man vs sentry

lookout man and sentry both are nouns.

Word	Noun	Adjective	Verb	Adverb
lookout man	Yes	No	No	No
sentry	Yes	No	No	No

As nouns, lookout man and sentry are synonyms defined as:

lookout man and sentry: a person employed to keep watch for some anticipated event

Other synonyms of lookout man include lookout, picket, scout, sentinel, spotter, watch.

lookout man (noun)	sentry (noun)
a person employed to keep watch for some anticipated event	a person employed to keep watch for some anticipated event