butterbean vs butter bean

butterbean and butter bean both are nouns.

Word	Noun	Adjective	Verb	Adverb
butterbean	Yes	No	No	No
butter bean	Yes	No	No	No

As nouns, butterbean and butter bean are synonyms defined as:

Other synonyms of butterbean include civet bean, sieva bean.

butterbean (noun)	butter bean (noun)
small flat green bean similar to lima beans	small flat green bean similar to lima beans
	bush bean plant cultivated especially in southern United States having small flat edible seeds