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.
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   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.
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   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.
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            Author of all being,
            Fountain of light, thyself invisible. --Milton.
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   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.
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The Collaborative International Dictionary of English v.0.48:

Tridacna \Tri*dac"na\, n. [L., pl., a kind of oysters, fr. Gr. ?
   eaten at three bites, ? tri- + ? to bite.] (Zool.)
   A genus of very large marine bivalve shells found on the
   coral reefs of the Indian and Pacific Oceans. One species
   (Tridacna gigas) often weighs four or five hundred pounds,
   and is sometimes used for baptismal fonts. Called also paw
   shell, and fountain shell.
   [1913 Webster] Tridactyl