strike down vs void

strike down is not a noun while void is a noun.

Word	Noun	Adjective	Verb	Adverb
strike down	No	No	Yes	No
void	Yes	Yes	Yes	No

As verbs, void is a hyponym of strike down; that is, void is a word with a more specific, narrower meaning than strike down:

strike down (noun)	void (noun)
	an empty area or space
	the state of nonexistence

strike down (adjective)	void (adjective)
	containing nothing
	lacking any legal or binding force

strike down (verb)	void (verb)
cause to fall by or as if by delivering a blow	excrete or discharge from the body
cause to die, especially suddenly	take away the legal force of or render ineffective
declare null and void; make ineffective	clear (a room, house, place) of occupants or empty or clear (a place or receptacle) of something
	declare invalid