The Collaborative International Dictionary of English v.0.48:

Sulphur \Sul"phur\, n. [L., better sulfur: cf. F. soufre.]
   1. (Chem.) A nonmetallic element occurring naturally in large
      quantities, either combined as in the sulphides (as
      pyrites) and sulphates (as gypsum), or native in volcanic
      regions, in vast beds mixed with gypsum and various earthy
      materials, from which it is melted out. Symbol S. Atomic
      weight 32. The specific gravity of ordinary octohedral
      sulphur is 2.05; of prismatic sulphur, 1.96.
      [1913 Webster]

   Note: It is purified by distillation, and is obtained as a
         lemon-yellow powder (by sublimation), called flour, or
         flowers, of sulphur, or in cast sticks called roll
         sulphur, or brimstone. It burns with a blue flame and a
         peculiar suffocating odor. It is an ingredient of
         gunpowder, is used on friction matches, and in medicine
         (as a laxative and insecticide), but its chief use is
         in the manufacture of sulphuric acid. Sulphur can be
         obtained in two crystalline modifications, in
         orthorhombic octahedra, or in monoclinic prisms, the
         former of which is the more stable at ordinary
         temperatures. Sulphur is the type, in its chemical
         relations, of a group of elements, including selenium
         and tellurium, called collectively the sulphur group,
         or family. In many respects sulphur resembles oxygen.
         [1913 Webster]

   2. (Zool.) Any one of numerous species of yellow or orange
      butterflies of the subfamily Pierinae; as, the clouded
      sulphur (Eurymus philodice syn. Colias philodice),
      which is the common yellow butterfly of the Eastern United
      States.
      [1913 Webster]

   Amorphous sulphur (Chem.), an elastic variety of sulphur of
      a resinous appearance, obtained by pouring melted sulphur
      into water. On standing, it passes back into a brittle
      crystalline modification.

   Liver of sulphur. (Old Chem.) See Hepar.

   Sulphur acid. (Chem.) See Sulphacid.

   Sulphur alcohol. (Chem.) See Mercaptan.

   Sulphur auratum [L.] (Old Chem.), a golden yellow powder,
      consisting of antimonic sulphide, Sb2S5, -- formerly a
      famous nostrum.

   Sulphur base (Chem.), an alkaline sulphide capable of
      acting as a base in the formation of sulphur salts
      according to the old dual theory of salts. [Archaic]

   Sulphur dioxide (Chem.), a colorless gas, SO2, of a
      pungent, suffocating odor, produced by the burning of
      sulphur. It is employed chiefly in the production of
      sulphuric acid, and as a reagent in bleaching; -- called
      also sulphurous anhydride, and formerly sulphurous
      acid.

   Sulphur ether (Chem.), a sulphide of hydrocarbon radicals,
      formed like the ordinary ethers, which are oxides, but
      with sulphur in the place of oxygen.

   Sulphur salt (Chem.), a salt of a sulphacid; a sulphosalt.


   Sulphur showers, showers of yellow pollen, resembling
      sulphur in appearance, often carried from pine forests by
      the wind to a great distance.

   Sulphur trioxide (Chem.), a white crystalline solid, SO3,
      obtained by oxidation of sulphur dioxide. It dissolves in
      water with a hissing noise and the production of heat,
      forming sulphuric acid, and is employed as a dehydrating
      agent. Called also sulphuric anhydride, and formerly
      sulphuric acid.

   Sulphur whale. (Zool.) See Sulphur-bottom.

   Vegetable sulphur (Bot.), lycopodium powder. See under
      Lycopodium.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sulphuric \Sul*phu"ric\, a. [Cf. F. sulfurique.]
   1. Of or pertaining to sulphur; as, a sulphuric smell.
      [1913 Webster]

   2. (Chem.) Derived from, or containing, sulphur;
      specifically, designating those compounds in which the
      element has a higher valence as contrasted with the
      sulphurous compounds; as, sulphuric acid.
      [1913 Webster]

   Sulphuric acid.
      (a) Sulphur trioxide (see under Sulphur); -- formerly so
          called on the dualistic theory of salts. [Obs.]
      (b) A heavy, corrosive, oily liquid, H2SO4, colorless
          when pure, but usually yellowish or brownish, produced
          by the combined action of sulphur dioxide, oxygen
          (from the air), steam, and nitric fumes. It attacks
          and dissolves many metals and other intractable
          substances, sets free most acids from their salts, and
          is used in the manufacture of hydrochloric and nitric
          acids, of soda, of bleaching powders, etc. It is also
          powerful dehydrating agent, having a strong affinity
          for water, and eating and corroding paper, wood,
          clothing, etc. It is thus used in the manufacture of
          ether, of imitation parchment, and of nitroglycerin.
          It is also used in etching iron, in removing iron
          scale from forgings, in petroleum refining, etc., and
          in general its manufacture is the most important and
          fundamental of all the chemical industries. Formerly
          called vitriolic acid, and now popularly vitriol,
          and oil of vitriol.

   Fuming sulphuric acid, or Nordhausen sulphuric acid. See
      Disulphuric acid, under Disulphuric.

   Sulphuric anhydride, sulphur trioxide. See under Sulphur.


   Sulphuric ether, common anaesthetic ether; -- so called
      because made by the catalytic action of sulphuric acid on
      alcohol. See Ether, 3
      (a) .
          [1913 Webster]

WordNet (r) 3.0 (2006):

sulphuric acid
    n 1: (H2SO4) a highly corrosive acid made from sulfur dioxide;
         widely used in the chemical industry [syn: vitriol, oil
         of vitriol, sulfuric acid, sulphuric acid]