Indian millet vs ricegrass

Indian millet and ricegrass both are nouns.

Word	Noun	Adjective	Verb	Adverb
Indian millet	Yes	No	No	No
ricegrass	Yes	No	No	No

As nouns, ricegrass is a hypernym of Indian millet; that is, ricegrass is a word with a broader meaning than Indian millet:

Indian millet: valuable forage grass of dry upland areas and plains of western North America to northern Mexico
ricegrass: any grass of the genus Oryzopsis

Other hypernyms of Indian millet include rice grass.

Indian millet (noun)	ricegrass (noun)
sorghums of dry regions of Asia and North Africa	any grass of the genus Oryzopsis
valuable forage grass of dry upland areas and plains of western North America to northern Mexico