zip gun vs pistol

zip gun and pistol both are nouns.

Word	Noun	Adjective	Verb	Adverb
zip gun	Yes	No	No	No
pistol	Yes	No	No	No

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

Other hypernyms of zip gun include handgun, shooting iron, side arm.

zip gun (noun)	pistol (noun)
a crude homemade pistol	a firearm that is held and fired with one hand