old witchgrass vs tumble grass

old witchgrass and tumble grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
old witchgrass	Yes	No	No	No
tumble grass	Yes	No	No	No

As nouns, old witchgrass and tumble grass are synonyms defined as:

old witchgrass and tumble grass: North American grass with slender brushy panicles; often a weed on cultivated land

Other synonyms of old witchgrass include old witch grass, Panicum capillare, witch grass, witchgrass.

old witchgrass (noun)	tumble grass (noun)
North American grass with slender brushy panicles; often a weed on cultivated land	North American grass with slender brushy panicles; often a weed on cultivated land