penny grass vs stinkweed

penny grass and stinkweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
penny grass	Yes	No	No	No
stinkweed	Yes	No	No	No

As nouns, penny grass and stinkweed are synonyms defined as:

penny grass and stinkweed: foetid Eurasian weed having round flat pods; naturalized throughout North America

Other synonyms of penny grass include fanweed, field pennycress, French weed, mithridate mustard, Thlaspi arvense.

penny grass (noun)	stinkweed (noun)
foetid Eurasian weed having round flat pods; naturalized throughout North America	foetid Eurasian weed having round flat pods; naturalized throughout North America