buckthorn vs ribgrass

buckthorn and ribgrass both are nouns.

Word	Noun	Adjective	Verb	Adverb
buckthorn	Yes	No	No	No
ribgrass	Yes	No	No	No

As nouns, buckthorn and ribgrass are synonyms defined as:

buckthorn and ribgrass: an Old World plantain with long narrow ribbed leaves widely established in temperate regions

buckthorn (noun)	ribgrass (noun)
any shrub or small tree of the genus Bumelia	an Old World plantain with long narrow ribbed leaves widely established in temperate regions
a shrub or shrubby tree of the genus Rhamnus; fruits are source of yellow dyes or pigments
an Old World plantain with long narrow ribbed leaves widely established in temperate regions