burp gun vs submachine gun

burp gun and submachine gun both are nouns.

Word	Noun	Adjective	Verb	Adverb
burp gun	Yes	No	No	No
submachine gun	Yes	No	No	No

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

burp gun (noun)	submachine gun (noun)
a fully automatic pistol; a small submachine gun	machine gun that is a portable automatic firearm