sentinel vs lookout man

sentinel and lookout man both are nouns.

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

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

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

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

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