banzai attack vs onrush

banzai attack and onrush both are nouns.

Word	Noun	Adjective	Verb	Adverb
banzai attack	Yes	No	No	No
onrush	Yes	No	No	No

As nouns, onrush is a hypernym of banzai attack; that is, onrush is a word with a broader meaning than banzai attack:

banzai attack: a mass attack of troops without concern for casualties; originated by Japanese who accompanied it with yells of `banzai'
onrush: (military) an offensive against an enemy (using weapons)

Other hypernyms of banzai attack include attack, onset, onslaught.

banzai attack (noun)	onrush (noun)
a mass attack of troops without concern for casualties; originated by Japanese who accompanied it with yells of `banzai'	(military) an offensive against an enemy (using weapons)
	a forceful forward rush or flow