black archangel vs stinking horehound

black archangel and stinking horehound both are nouns.

Word	Noun	Adjective	Verb	Adverb
black archangel	Yes	No	No	No
stinking horehound	Yes	No	No	No

As nouns, black archangel and stinking horehound are synonyms defined as:

black archangel and stinking horehound: ill-smelling European herb with rugose leaves and whorls of dark purple flowers

Other synonyms of black archangel include Ballota nigra, black horehound, fetid horehound.

black archangel (noun)	stinking horehound (noun)
ill-smelling European herb with rugose leaves and whorls of dark purple flowers	ill-smelling European herb with rugose leaves and whorls of dark purple flowers