The Collaborative International Dictionary of English v.0.48:

millet \mil"let\ (m[i^]l"l[e^]t), n. [F., dim. of mil, L.
   milium; akin to Gr. meli`nh, AS. mil.] (Bot.)
   The name of several cereal and forage grasses which bear an
   abundance of small roundish grains. The common millets of
   Germany and Southern Europe are Panicum miliaceum, and
   Setaria Italica.

   Note:

   Arabian millet is Sorghum Halepense.

   Egyptian millet or

   East Indian millet is Penicillaria spicata.

   Indian millet is Sorghum vulgare. (See under Indian.)


   Italian millet is Setaria Italica, a coarse, rank-growing
      annual grass, valuable for fodder when cut young, and
      bearing nutritive seeds; -- called also Hungarian grass.


   Texas millet is Panicum Texanum.

   Wild millet, or

   Millet grass, is Milium effusum, a tall grass growing in
      woods.
      [1913 Webster]

WordNet (r) 3.0 (2006):

millet
    n 1: any of various small-grained annual cereal and forage
         grasses of the genera Panicum, Echinochloa, Setaria,
         Sorghum, and Eleusine
    2: French painter of rural scenes (1814-1875) [syn: Millet,
       Jean Francois Millet]
    3: small seed of any of various annual cereal grasses especially
       Setaria italica