smut grass vs dropseed

smut grass and dropseed both are nouns.

Word	Noun	Adjective	Verb	Adverb
smut grass	Yes	No	No	No
dropseed	Yes	No	No	No

As nouns, dropseed is a hypernym of smut grass; that is, dropseed is a word with a broader meaning than smut grass:

smut grass: grass native to West Indies but common in southern United States having tufted wiry stems often infested with a dark fungus
dropseed: a grass of the genus Sporobolus

Other hypernyms of smut grass include drop-seed.

smut grass (noun)	dropseed (noun)
grass native to West Indies but common in southern United States having tufted wiry stems often infested with a dark fungus	a grass of the genus Sporobolus