The Collaborative International Dictionary of English v.0.48:

Sugar \Sug"ar\, n. [OE. sugre, F. sucre (cf. It. zucchero, Sp.
   az['u]car), fr. Ar. sukkar, assukkar, fr. Skr. [,c]arkar[=a]
   sugar, gravel; cf. Per. shakar. Cf. Saccharine, Sucrose.]
   1. A sweet white (or brownish yellow) crystalline substance,
      of a sandy or granular consistency, obtained by
      crystallizing the evaporated juice of certain plants, as
      the sugar cane, sorghum, beet root, sugar maple, etc. It
      is used for seasoning and preserving many kinds of food
      and drink. Ordinary sugar is essentially sucrose. See the
      Note below.
      [1913 Webster]

   Note: The term sugar includes several commercial grades, as
         the white or refined, granulated, loaf or lump, and the
         raw brown or muscovado. In a more general sense, it
         includes several distinct chemical compounds, as the
         glucoses, or grape sugars (including glucose proper,
         dextrose, and levulose), and the sucroses, or true
         sugars (as cane sugar). All sugars are carbohydrates.
         See Carbohydrate. The glucoses, or grape sugars, are
         ketone alcohols of the formula C6H12O6, and they turn
         the plane of polarization to the right or the left.
         They are produced from the amyloses and sucroses, as by
         the action of heat and acids of ferments, and are
         themselves decomposed by fermentation into alcohol and
         carbon dioxide. The only sugar (called acrose) as yet
         produced artificially belongs to this class. The
         sucroses, or cane sugars, are doubled glucose
         anhydrides of the formula C12H22O11. They are usually
         not fermentable as such (cf. Sucrose), and they act
         on polarized light.
         [1913 Webster]

   2. By extension, anything resembling sugar in taste or
      appearance; as, sugar of lead (lead acetate), a poisonous
      white crystalline substance having a sweet taste.
      [1913 Webster]

   3. Compliment or flattery used to disguise or render
      acceptable something obnoxious; honeyed or soothing words.
      [Colloq.]
      [1913 Webster]

   Acorn sugar. See Quercite.

   Cane sugar, sugar made from the sugar cane; sucrose, or an
      isomeric sugar. See Sucrose.

   Diabetes sugar, or Diabetic sugar (Med. Chem.), a variety
      of sugar (grape sugar or dextrose) excreted in the urine
      in diabetes mellitus; -- the presence of such a sugar in
      the urine is used to diagnose the illness.

   Fruit sugar. See under Fruit, and Fructose.

   Grape sugar, a sirupy or white crystalline sugar (dextrose
      or glucose) found as a characteristic ingredient of ripe
      grapes, and also produced from many other sources. See
      Dextrose, and Glucose.

   Invert sugar. See under Invert.

   Malt sugar, a variety of sugar isomeric with sucrose, found
      in malt. See Maltose.

   Manna sugar, a substance found in manna, resembling, but
      distinct from, the sugars. See Mannite.

   Milk sugar, a variety of sugar characteristic of fresh
      milk, and isomeric with sucrose. See Lactose.

   Muscle sugar, a sweet white crystalline substance isomeric
      with, and formerly regarded to, the glucoses. It is found
      in the tissue of muscle, the heart, liver, etc. Called
      also heart sugar. See Inosite.

   Pine sugar. See Pinite.

   Starch sugar (Com. Chem.), a variety of dextrose made by
      the action of heat and acids on starch from corn,
      potatoes, etc.; -- called also potato sugar, corn
      sugar, and, inaccurately, invert sugar. See Dextrose,
      and Glucose.

   Sugar barek, one who refines sugar.

   Sugar beet (Bot.), a variety of beet (Beta vulgaris) with
      very large white roots, extensively grown, esp. in Europe,
      for the sugar obtained from them.

   Sugar berry (Bot.), the hackberry.

   Sugar bird (Zool.), any one of several species of small
      South American singing birds of the genera Coereba,
      Dacnis, and allied genera belonging to the family
      Coerebidae. They are allied to the honey eaters.

   Sugar bush. See Sugar orchard.

   Sugar camp, a place in or near a sugar orchard, where maple
      sugar is made.

   Sugar candian, sugar candy. [Obs.]

   Sugar candy, sugar clarified and concreted or crystallized;
      candy made from sugar.

   Sugar cane (Bot.), a tall perennial grass (Saccharum
      officinarium), with thick short-jointed stems. It has
      been cultivated for ages as the principal source of sugar.


   Sugar loaf.
      (a) A loaf or mass of refined sugar, usually in the form
          of a truncated cone.
      (b) A hat shaped like a sugar loaf.
          [1913 Webster]

                Why, do not or know you, grannam, and that sugar
                loaf?                             --J. Webster.
          [1913 Webster]

   Sugar maple (Bot.), the rock maple (Acer saccharinum).
      See Maple.

   Sugar mill, a machine for pressing out the juice of the
      sugar cane, usually consisting of three or more rollers,
      between which the cane is passed.

   Sugar mite. (Zool.)
      (a) A small mite (Tyroglyphus sacchari), often found in
          great numbers in unrefined sugar.
      (b) The lepisma.

   Sugar of lead. See Sugar, 2, above.

   Sugar of milk. See under Milk.

   Sugar orchard, a collection of maple trees selected and
      preserved for purpose of obtaining sugar from them; --
      called also, sometimes, sugar bush. [U.S.] --Bartlett.

   Sugar pine (Bot.), an immense coniferous tree (Pinus
      Lambertiana) of California and Oregon, furnishing a soft
      and easily worked timber. The resinous exudation from the
      stumps, etc., has a sweetish taste, and has been used as a
      substitute for sugar.

   Sugar squirrel (Zool.), an Australian flying phalanger
      (Belideus sciureus), having a long bushy tail and a
      large parachute. It resembles a flying squirrel. See
      Illust. under Phlanger.

   Sugar tongs, small tongs, as of silver, used at table for
      taking lumps of sugar from a sugar bowl.

   Sugar tree. (Bot.) See Sugar maple, above.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sugar beet
    n 1: form of the common beet having a sweet white root from
         which sugar is obtained
    2: white-rooted beet grown as a source of sugar