squirt gun vs water gun

squirt gun and water gun both are nouns.

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

As nouns, squirt gun and water gun are synonyms defined as:

squirt gun and water gun: plaything consisting of a toy pistol that squirts water

Other synonyms of squirt gun include squirter, water pistol.

squirt gun (noun)	water gun (noun)
plaything consisting of a toy pistol that squirts water	plaything consisting of a toy pistol that squirts water