Source : Webster's Revised Unabridged Dictionary (1913)

Johnson grass \John"son grass`\ [Named after W. Johnson of
   Alabama, who planted it about 1840-1845.] (Bot.)
   A tall perennial grass ({Sorghum Halepense}), valuable in the
   Southern and Western States for pasture and hay. The
   rootstocks are large and juicy and are eagerly sought by
   swine. Called also {Cuba grass}, {Means grass}, {Evergreen
   millet}, and {Arabian millet}.



   Note:

   {Arabian millet} is {Sorghum Halepense}.

   {Egyptian 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 tail grass growing in
      woods.

Aleppo grass \Aleppo grass\ (Bot.)
   One of the cultivated forms of {Andropogon Halepensis} (syn.
   {Sorghum Halepense}). See {Andropogon}, below.

Sorghum \Sor"ghum\, n. [NL., probably of Chinese origin.] (Bot.)
   (a) A genus of grasses, properly limited to two species,
       {Sorghum Halepense}, the Arabian millet, or Johnson grass
       (see {Johnson grass}), and {S. vulgare}, the Indian
       millet (see {Indian millet}, under {Indian}).
   (b) A variety of {Sorghum vulgare}, grown for its saccharine
       juice; the Chinese sugar cane.

Grama grass, grazing. West and Pacific slope. {Bouteloua
oligostachya}, etc. Great bunch grass, pasture and hay. Far
West. {Festuca scabrella}. Guinea grass, hay. South. {Panicum
jumentorum}. Herd's grass, in New England Timothy, in
Pennsylvania and South Redtop. Indian grass. Same as {Wood
grass} (below). Italian rye grass, forage and hay. {Lolium
Italicum}. Johnson grass, grazing aud hay. South and Southwest.
{Sorghum Halepense}. Kentucky blue grass, pasture. {Poa
pratensis}. Lyme grass, coarse hay. South. {Elymus}, several
species. Manna grass, pasture and hay. {Glyceria}, several
species. Meadow fescue, pasture and hay. {Festuca elatior}.
Meadow foxtail, pasture, hay, lawn. North. {Alopecurus
pratensis}. Meadow grass, pasture, hay, lawn. {Poa}, several
species. Mesquite, or Muskit grass. Same as {Grama grass}
(above).

Source : WordNet®

Sorghum halepense
     n : tall perennial grass that spreads by creeping rhizomes and
         is grown for fodder; naturalized in southern United
         States where it is a serious pest on cultivated land
         [syn: {Johnson grass}, {Aleppa grass}, {means grass}, {evergreen
         millet}, {Sorghum halapense}]