broad bean vs horse bean

broad bean and horse bean both are nouns.

Word	Noun	Adjective	Verb	Adverb
broad bean	Yes	No	No	No
horse bean	Yes	No	No	No

As nouns, broad bean and horse bean are synonyms defined as:

broad bean and horse bean: a bean plant cultivated for use animal fodder

broad bean (noun)	horse bean (noun)
shell beans cooked as lima beans	a bean plant cultivated for use animal fodder
a bean plant cultivated for use animal fodder
Old World upright plant grown especially for its large flat edible seeds but also as fodder
seed of the broad-bean plant