lumber vs strike down

lumber is a noun but strike down is not a noun.

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

As verbs, strike down is a hypernym of lumber; that is, strike down is a word with a broader meaning than lumber:

Other hypernyms of lumber include cut down, drop, fell.

lumber (noun)	strike down (noun)
an implement used in baseball by the batter
the wood of trees cut and prepared for use as building material

lumber (verb)	strike down (verb)
cut lumber, as in woods and forests	cause to fall by or as if by delivering a blow
move heavily or clumsily	cause to die, especially suddenly
	declare null and void; make ineffective