stupid vs unthinking

stupid is a noun but unthinking is not a noun.

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

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

stupid (adjective)	unthinking (adjective)
lacking or marked by lack of intellectual acuity	without care or thought for others
lacking intelligence	mentally sluggish
in a state of mental numbness especially as resulting from shock	not exhibiting or characterized by careful thought

stupid (adverb)	unthinking (adverb)
	in a thoughtless manner