harpoon gun vs cannon

harpoon gun and cannon both are nouns.

Word	Noun	Adjective	Verb	Adverb
harpoon gun	Yes	No	No	No
cannon	Yes	No	Yes	No

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

harpoon gun (noun)	cannon (noun)
a cannon or similar gun that fires harpoons	a shot in billiards in which the cue ball contacts one object ball and then the other
	lower part of the leg extending from the hock to the fetlock in hoofed mammals
	a large artillery gun that is usually on wheels
	heavy automatic gun fired from an airplane
	(Middle Ages) a cylindrical piece of armor plate to protect the arm
	heavy gun fired from a tank

harpoon gun (verb)	cannon (verb)
	fire a cannon
	make a cannon