bank guard vs watcher

bank guard and watcher both are nouns.

Word	Noun	Adjective	Verb	Adverb
bank guard	Yes	No	No	No
watcher	Yes	No	No	No

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

Other hypernyms of bank guard include security guard, watchman.

bank guard (noun)	watcher (noun)
a security guard at a bank	a guard who keeps watch
	a close observer; someone who looks at something (such as an exhibition of some kind)
	a person who keeps a devotional vigil by a sick bed or by a dead body