oddball vs whacko

oddball and whacko both are nouns.

Word	Noun	Adjective	Verb	Adverb
oddball	Yes	No	No	No
whacko	Yes	No	No	No

As nouns, whacko is a hyponym of oddball; that is, whacko is a word with a more specific, narrower meaning than oddball:

Other hyponyms of oddball include crackpot, crank, fruitcake, nut, nut case, screwball, nutter, wacko.

oddball (noun)	whacko (noun)
a person with an unusual or odd personality	a person who is regarded as eccentric or mad