watcher vs bank guard

watcher and bank guard both are nouns.

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

As nouns, bank guard is a hyponym of watcher; that is, bank guard is a word with a more specific, narrower meaning than watcher:

watcher (noun)	bank guard (noun)
a guard who keeps watch	a security guard at a bank
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