headless vs stupid

headless is not a noun while stupid is a noun.

Word	Noun	Adjective	Verb	Adverb
headless	No	Yes	No	No
stupid	Yes	Yes	No	No

headless (noun)	stupid (noun)
	a person who is not very bright

headless (adjective)	stupid (adjective)
not having a head or formed without a head	lacking or marked by lack of intellectual acuity
not using intelligence	lacking intelligence
	in a state of mental numbness especially as resulting from shock