The Collaborative International Dictionary of English v.0.48:

Fountain \Foun"tain\ (foun"t[i^]n), n. [F. fontaine, LL.
   fontana, fr. L. fons, fontis. See 2d Fount.]
   1. A spring of water issuing from the earth.
      [1913 Webster]

   2. An artificially produced jet or stream of water; also, the
      structure or works in which such a jet or stream rises or
      flows; a basin built and constantly supplied with pure
      water for drinking and other useful purposes, or for
      ornament.
      [1913 Webster]

   3. A reservoir or chamber to contain a liquid which can be
      conducted or drawn off as needed for use; as, the ink
      fountain in a printing press, etc.
      [1913 Webster]

   4. The source from which anything proceeds, or from which
      anything is supplied continuously; origin; source.
      [1913 Webster]

            Judea, the fountain of the gospel.    --Fuller.
      [1913 Webster]

            Author of all being,
            Fountain of light, thyself invisible. --Milton.
      [1913 Webster]

   Air fountain. See under Air.

   Fountain heead, primary source; original; first principle.
      --Young.

   Fountain inkstand, an inkstand having a continual supply of
      ink, as from elevated reservoir.

   Fountain lamp, a lamp fed with oil from an elevated
      reservoir.

   Fountain pen, a pen with a reservoir in the handle which
      furnishes a supply of ink.

   Fountain pump.
      (a) A structure for a fountain, having the form of a pump.
      (b) A portable garden pump which throws a jet, for
          watering plants, etc.

   Fountain shell (Zool.), the large West Indian conch shell
      (Strombus gigas).

   Fountain of youth, a mythical fountain whose waters were
      fabled to have the property of renewing youth.
      [1913 Webster]

WordNet (r) 3.0 (2006):

fountain
    n 1: a structure from which an artificially produced jet of
         water arises
    2: a natural flow of ground water [syn: spring, fountain,
       outflow, outpouring, natural spring]
    3: an artificially produced flow of water [syn: fountain,
       jet]
    4: a plumbing fixture that provides a flow of water [syn:
       fountain, fount]