firing vs onslaught

firing and onslaught both are nouns.

Word	Noun	Adjective	Verb	Adverb
firing	Yes	No	No	No
onslaught	Yes	No	No	No

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

Other hypernyms of firing include attack, onrush, onset.

firing (noun)	onslaught (noun)
the act of setting something on fire	(military) an offensive against an enemy (using weapons)
the termination of someone's employment (leaving them free to depart)	the rapid and continuous delivery of linguistic communication (spoken or written)
the act of discharging a gun	a sudden and severe onset of trouble
the act of firing weapons or artillery at an enemy