cuckooflower vs bitter cress

cuckooflower and bitter cress both are nouns.

Word	Noun	Adjective	Verb	Adverb
cuckooflower	Yes	No	No	No
bitter cress	Yes	No	No	No

As nouns, bitter cress is a hypernym of cuckooflower; that is, bitter cress is a word with a broader meaning than cuckooflower:

cuckooflower: a bitter cress of Europe and America
bitter cress: any of various herbs of the genus Cardamine, having usually pinnate leaves and racemes of white, pink or purple flowers; cosmopolitan except Antarctic

Other hypernyms of cuckooflower include bittercress.

cuckooflower (noun)	bitter cress (noun)
a bitter cress of Europe and America	any of various herbs of the genus Cardamine, having usually pinnate leaves and racemes of white, pink or purple flowers; cosmopolitan except Antarctic