broad-bean vs shell bean plant

broad-bean and shell bean plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
broad-bean	Yes	No	No	No
shell bean plant	Yes	No	No	No

As nouns, shell bean plant is a hypernym of broad-bean; that is, shell bean plant is a word with a broader meaning than broad-bean:

broad-bean: Old World upright plant grown especially for its large flat edible seeds but also as fodder
shell bean plant: a bean plant grown primarily for its edible seed rather than its pod

Other hypernyms of broad-bean include shell bean.

broad-bean (noun)	shell bean plant (noun)
Old World upright plant grown especially for its large flat edible seeds but also as fodder	a bean plant grown primarily for its edible seed rather than its pod