The Collaborative International Dictionary of English v.0.48:

Fund \Fund\, n. [OF. font, fond, nom. fonz, bottom, ground, F.
   fond bottom, foundation, fonds fund, fr. L. fundus bottom,
   ground, foundation, piece of land. See Found to establish.]
   1. An aggregation or deposit of resources from which supplies
      are or may be drawn for carrying on any work, or for
      maintaining existence.
      [1913 Webster]

   2. A stock or capital; a sum of money appropriated as the
      foundation of some commercial or other operation
      undertaken with a view to profit; that reserve by means of
      which expenses and credit are supported; as, the fund of a
      bank, commercial house, manufacturing corporation, etc.
      [1913 Webster]

   3. pl. The stock of a national debt; public securities;
      evidences (stocks or bonds) of money lent to government,
      for which interest is paid at prescribed intervals; --
      called also public funds.
      [1913 Webster]

   4. An invested sum, whose income is devoted to a specific
      object; as, the fund of an ecclesiastical society; a fund
      for the maintenance of lectures or poor students; also,
      money systematically collected to meet the expenses of
      some permanent object.
      [1913 Webster]

   5. A store laid up, from which one may draw at pleasure; a
      supply; a full provision of resources; as, a fund of
      wisdom or good sense.
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            An inexhaustible fund of stories.     --Macaulay.
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   Sinking fund, the aggregate of sums of money set apart and
      invested, usually at fixed intervals, for the
      extinguishment of the debt of a government, or of a
      corporation, by the accumulation of interest.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sinking \Sink"ing\,
   a. & n. from Sink.
   [1913 Webster]

   Sinking fund. See under Fund.

   Sinking head (Founding), a riser from which the mold is fed
      as the casting shrinks. See Riser, n., 4.

   Sinking pump, a pump which can be lowered in a well or a
      mine shaft as the level of the water sinks.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sinking fund
    n 1: a fund accumulated regularly in a separate account and used
         to redeem debt securities

Bouvier's Law Dictionary, Revised 6th Ed (1856):

SINKING FUND. A fund arising from particular taxes, imposts, or duties,
which is appropriated towards the payment of the interest due on a public
loan and for the gradual payment of the principal. See Funding System.