lookout vs security guard

lookout and security guard both are nouns.

Word	Noun	Adjective	Verb	Adverb
lookout	Yes	No	No	No
security guard	Yes	No	No	No

As nouns, security guard is a hypernym of lookout; that is, security guard is a word with a broader meaning than lookout:

Other hypernyms of lookout include watcher, watchman.

lookout (noun)	security guard (noun)
the act of looking out	a guard who keeps watch
a structure commanding a wide view of its surroundings
an elevated post affording a wide view
a person employed to keep watch for some anticipated event