large crabgrass vs finger grass

large crabgrass and finger grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
large crabgrass	Yes	No	No	No
finger grass	Yes	No	No	No

As nouns, finger grass is a hypernym of large crabgrass; that is, finger grass is a word with a broader meaning than large crabgrass:

large crabgrass: a European forage grass grown for hay; a naturalized weed in United States
finger grass: grasses with creeping stems that root freely; a pest in lawns

Other hypernyms of large crabgrass include crab grass, crabgrass.

large crabgrass (noun)	finger grass (noun)
a European forage grass grown for hay; a naturalized weed in United States	any grass of the genus Chloris; occurs in short grassland especially on waste ground or poor soils
	grasses with creeping stems that root freely; a pest in lawns