water gun vs toy

water gun and toy both are nouns.

Word	Noun	Adjective	Verb	Adverb
water gun	Yes	No	No	No
toy	Yes	No	Yes	No

As nouns, toy is a hypernym of water gun; that is, toy is a word with a broader meaning than water gun:

Other hypernyms of water gun include plaything.

water gun (noun)	toy (noun)
plaything consisting of a toy pistol that squirts water	any of several breeds of very small dogs kept purely as pets
	an artifact designed to be played with
	a copy that reproduces a person or thing in greatly reduced size
	a nonfunctional replica of something else (frequently used as a modifier)
	a device regarded as providing amusement

water gun (verb)	toy (verb)
	engage in an activity as if it were a game rather than take it seriously
	manipulate manually or in one's mind or imagination
	behave carelessly or indifferently