screwball vs eccentric

screwball and eccentric both are nouns.

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

As nouns, eccentric is a hypernym of screwball; that is, eccentric is a word with a broader meaning than screwball:

Other hypernyms of screwball include eccentric person, flake, geek, oddball.

screwball (noun)	eccentric (noun)
a pitch with reverse spin that curves toward the side of the plate from which it was thrown	a person with an unusual or odd personality
a whimsically eccentric person	a person of a specified kind (usually with many eccentricities)

screwball (adjective)	eccentric (adjective)
foolish; totally unsound	not having a common center; not concentric
	conspicuously or grossly unconventional or unusual