strike down vs cancel

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

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

As verbs, strike down and cancel are synonyms defined as:

strike down (noun)	cancel (noun)
	a notation cancelling a previous sharp or flat

strike down (verb)	cancel (verb)
cause to fall by or as if by delivering a blow	make invalid for use
cause to die, especially suddenly	remove or make invisible
declare null and void; make ineffective	declare null and void; make ineffective
	postpone indefinitely or annul something that was scheduled
	make up for