quack grass vs couch grass

quack grass and couch grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
quack grass	Yes	No	No	No
couch grass	Yes	No	No	No

As nouns, quack grass and couch grass are synonyms defined as:

quack grass and couch grass: European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed

Other synonyms of quack grass include Agropyron repens, dog grass, quackgrass, quick grass, witch grass, witchgrass.

quack grass (noun)	couch grass (noun)
European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed	European grass spreading rapidly by creeping rhizomes; naturalized in North America as a weed