fruitcake vs screwball

fruitcake and screwball both are nouns.

Word	Noun	Adjective	Verb	Adverb
fruitcake	Yes	No	No	No
screwball	Yes	Yes	No	No

As nouns, fruitcake and screwball are synonyms defined as:

Other synonyms of fruitcake include crackpot, crank, nut, nut case.

fruitcake (noun)	screwball (noun)
a rich cake containing dried fruit and nuts and citrus peel and so on	a pitch with reverse spin that curves toward the side of the plate from which it was thrown
a whimsically eccentric person	a whimsically eccentric person

fruitcake (adjective)	screwball (adjective)
	foolish; totally unsound