patroller vs security guard

patroller and security guard both are nouns.

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

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

patroller: someone on patrol duty; an individual or a member of a group that patrols an area
security guard: a guard who keeps watch

Other hypernyms of patroller include watcher, watchman.

patroller (noun)	security guard (noun)
someone on patrol duty; an individual or a member of a group that patrols an area	a guard who keeps watch