tall oat grass vs false oat

tall oat grass and false oat both are nouns.

Word	Noun	Adjective	Verb	Adverb
tall oat grass	Yes	No	No	No
false oat	Yes	No	No	No

As nouns, tall oat grass and false oat are synonyms defined as:

tall oat grass and false oat: coarse perennial Eurasian grass resembling oat; found on roadside verges and rough grassland and in hay meadows; introduced in North America for forage

Other synonyms of tall oat grass include Arrhenatherum elatius, evergreen grass, French rye, tall meadow grass.

tall oat grass (noun)	false oat (noun)
coarse perennial Eurasian grass resembling oat; found on roadside verges and rough grassland and in hay meadows; introduced in North America for forage	coarse perennial Eurasian grass resembling oat; found on roadside verges and rough grassland and in hay meadows; introduced in North America for forage