lumber room vs storeroom

lumber room and storeroom both are nouns.

Word	Noun	Adjective	Verb	Adverb
lumber room	Yes	No	No	No
storeroom	Yes	No	No	No

As nouns, storeroom is a hypernym of lumber room; that is, storeroom is a word with a broader meaning than lumber room:

lumber room: a storeroom in a house where odds and ends can be stored (especially furniture)
storeroom: a room in which things are stored

Other hypernyms of lumber room include storage room, stowage.

lumber room (noun)	storeroom (noun)
a storeroom in a house where odds and ends can be stored (especially furniture)	a room in which things are stored