bristlegrass vs bristle grass

bristlegrass and bristle grass both are nouns.

Word	Noun	Adjective	Verb	Adverb
bristlegrass	Yes	No	No	No
bristle grass	Yes	No	No	No

As nouns, bristlegrass and bristle grass are synonyms defined as:

bristlegrass and bristle grass: grasses of grasslands and woodlands having large gracefully arching spikes with long bristles beneath each spikelet

bristlegrass (noun)	bristle grass (noun)
grasses of grasslands and woodlands having large gracefully arching spikes with long bristles beneath each spikelet	grasses of grasslands and woodlands having large gracefully arching spikes with long bristles beneath each spikelet