butterball vs Bucephela albeola

butterball and Bucephela albeola both are nouns.

Word	Noun	Adjective	Verb	Adverb
butterball	Yes	No	No	No
Bucephela albeola	Yes	No	No	No

As nouns, butterball and Bucephela albeola are synonyms defined as:

butterball and Bucephela albeola: small North American diving duck; males have bushy head plumage

Other synonyms of butterball include bufflehead, dipper.

butterball (noun)	Bucephela albeola (noun)
small North American diving duck; males have bushy head plumage	small North American diving duck; males have bushy head plumage
a rotund individual