As nouns the difference between grass and millet
is that
grass is (countable|uncountable) any plant of the family poaceae, characterized by leaves that arise from nodes in the stem and leaf bases that wrap around the stem, especially those grown as ground cover rather than for grain while
millet is any of a group of various types of grass or its grains used as food or
millet can be (historical) a semi-autonomous confessional community under the ottoman empire,
especially a non-muslim one.
As a verb grass
is to lay out on the grass; to knock down (an opponent etc).