plumbago vs black lead

plumbago and black lead both are nouns.

Word	Noun	Adjective	Verb	Adverb
plumbago	Yes	No	No	No
black lead	Yes	No	No	No

As nouns, plumbago and black lead are synonyms defined as:

plumbago and black lead: used as a lubricant and as a moderator in nuclear reactors

Other synonyms of plumbago include graphite.

plumbago (noun)	black lead (noun)
any plumbaginaceous plant of the genus Plumbago	used as a lubricant and as a moderator in nuclear reactors
used as a lubricant and as a moderator in nuclear reactors