indirect fire vs firing

indirect fire and firing both are nouns.

Word	Noun	Adjective	Verb	Adverb
indirect fire	Yes	No	No	No
firing	Yes	No	No	No

As nouns, firing is a hypernym of indirect fire; that is, firing is a word with a broader meaning than indirect fire:

indirect fire: fire delivered on a target that is not itself used as the point of aim for the weapons
firing: the act of firing weapons or artillery at an enemy

Other hypernyms of indirect fire include fire.

indirect fire (noun)	firing (noun)
fire delivered on a target that is not itself used as the point of aim for the weapons	the act of setting something on fire
	the termination of someone's employment (leaving them free to depart)
	the act of discharging a gun
	the act of firing weapons or artillery at an enemy