American spelling vs lackluster

American spelling is a noun but lackluster is not a noun.

Word	Noun	Adjective	Verb	Adverb
American spelling	Yes	No	No	No
lackluster	No	Yes	No	No

American spelling (noun)	lackluster (noun)
English orthography used in the United States (characterized by 'analyze', 'center', 'usable')

American spelling (adjective)	lackluster (adjective)
	lacking luster or shine
	lacking brilliance or vitality