The Collaborative International Dictionary of English v.0.48:

Soda \So"da\, n. [It., soda, in OIt., ashes used in making
   glass, fr. L. solida, fem. of solidus solid; solida having
   probably been a name of glasswort. See Solid.]
   1. (Chem.)
      (a) Sodium oxide or hydroxide.
      (b) Popularly, sodium carbonate or bicarbonate. Sodium
          bicarbonate is also called baking soda
          [1913 Webster]

   2. same as sodium, used in terms such as bicarbonate of
      soda.
      [PJC]

   3. same as soda water.
      [PJC]

   4. a non-alcoholic beverage, sweetened by various means,
      containing flavoring and supersaturated with carbon
      dioxide, so as to be effervescent when the container is
      opened; -- in different localities it is variously called
      also soda pop, pop, mineral water, and minerals.
      It has many variants. The sweetening agent may be natural,
      such as cane sugar or corn syrup, or artificial, such as
      saccharin or aspartame. The flavoring varies widely,
      popular variants being fruit or cola flavoring.
      [PJC]

   Caustic soda, sodium hydroxide.

   Cooking soda, sodium bicarbonate. [Colloq.]

   Sal soda. See Sodium carbonate, under Sodium.

   Soda alum (Min.), a mineral consisting of the hydrous
      sulphate of alumina and soda.

   Soda ash, crude sodium carbonate; -- so called because
      formerly obtained from the ashes of sea plants and certain
      other plants, as saltwort (Salsola). See under Sodium.


   Soda fountain, an apparatus for drawing soda water, fitted
      with delivery tube, faucets, etc.

   Soda lye, a lye consisting essentially of a solution of
      sodium hydroxide, used in soap making.

   Soda niter. See Nitratine.

   Soda salts, salts having sodium for the base; specifically,
      sodium sulphate or Glauber's salts.

   Soda waste, the waste material, consisting chiefly of
      calcium hydroxide and sulphide, which accumulates as a
      useless residue or side product in the ordinary Leblanc
      process of soda manufacture; -- called also alkali
      waste.

   Washing soda, sodium carbonate. [Colloq.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Soda fountain \So"da foun`tain\, n.
   a counter at which people may sit and be served soda pop, ice
   cream, or light meals. Such counters may be located for
   example in restaurants, ice cream shops, drugstores,
   departments stores.
   [PJC]

WordNet (r) 3.0 (2006):

soda fountain
    n 1: a counter where ice cream and sodas and sundaes are
         prepared and served
    2: an apparatus for dispensing soda water