bombardment vs onslaught

bombardment and onslaught both are nouns.

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

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

Other hypernyms of bombardment include attack, onrush, onset.

As nouns, bombardment and onslaught are synonyms defined as:

bombardment and onslaught: the rapid and continuous delivery of linguistic communication (spoken or written)

Other synonyms of bombardment include barrage, outpouring.

bombardment (noun)	onslaught (noun)
the heavy fire of artillery to saturate an area rather than hit a specific target	(military) an offensive against an enemy (using weapons)
an attack by dropping bombs	the rapid and continuous delivery of linguistic communication (spoken or written)
the act (or an instance) of subjecting a body or substance to the impact of high-energy particles (as electrons or alpha rays)	a sudden and severe onset of trouble
the rapid and continuous delivery of linguistic communication (spoken or written)