sentry vs lookout man

sentry and lookout man both are nouns.

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

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

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

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

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