finger grass vs crab grass

finger grass and crab grass both are nouns.

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

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

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

Other synonyms of finger grass include crabgrass.

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