crab grass vs finger grass

crab grass and finger grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
crab grass	Yes	No	No	No
finger grass	Yes	No	No	No

As nouns, crab grass and finger grass are synonyms defined as:

crab grass and finger grass: grasses with creeping stems that root freely; a pest in lawns

Other synonyms of crab grass include crabgrass.

crab grass (noun)	finger grass (noun)
grasses with creeping stems that root freely; a pest in lawns	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