half-baked vs screwball

half-baked is not a noun while screwball is a noun.

Word	Noun	Adjective	Verb	Adverb
half-baked	No	Yes	No	No
screwball	Yes	Yes	No	No

As adjectives, half-baked and screwball are synonyms defined as:

Other synonyms of half-baked include crazy, softheaded.

half-baked (noun)	screwball (noun)
	a pitch with reverse spin that curves toward the side of the plate from which it was thrown
	a whimsically eccentric person

half-baked (adjective)	screwball (adjective)
foolish; totally unsound	foolish; totally unsound
insufficiently cooked