The Collaborative International Dictionary of English v.0.48:

Apple \Ap"ple\ ([a^]p"p'l), n. [OE. appel, eppel, AS. [ae]ppel,
   [ae]pl; akin to Fries. & D. appel, OHG, aphul, aphol, G.
   apfel, Icel. epli, Sw. [aum]ple, Dan. [ae]ble, Gael. ubhall,
   W. afal, Arm. aval, Lith. ob[*u]lys, Russ. iabloko; of
   unknown origin.]
   1. The fleshy pome or fruit of a rosaceous tree (Pyrus
      malus) cultivated in numberless varieties in the
      temperate zones.
      [1913 Webster]

   Note: The European crab apple is supposed to be the original
         kind, from which all others have sprung.
         [1913 Webster]

   2. (bot.) Any tree genus Pyrus which has the stalk sunken
      into the base of the fruit; an apple tree.
      [1913 Webster]

   3. Any fruit or other vegetable production resembling, or
      supposed to resemble, the apple; as, apple of love, or
      love apple (a tomato), balsam apple, egg apple, oak apple.
      [1913 Webster]

   4. Anything round like an apple; as, an apple of gold.
      [1913 Webster]

   Note: Apple is used either adjectively or in combination; as,
         apple paper or apple-paper, apple-shaped, apple
         blossom, apple dumpling, apple pudding.
         [1913 Webster]

   Apple blight, an aphid which injures apple trees. See
      Blight, n.

   Apple borer (Zool.), a coleopterous insect (Saperda
      candida or Saperda bivittata), the larva of which bores
      into the trunk of the apple tree and pear tree.

   Apple brandy, brandy made from apples.

   Apple butter, a sauce made of apples stewed down in cider.
      --Bartlett.

   Apple corer, an instrument for removing the cores from
      apples.

   Apple fly (Zool.), any dipterous insect, the larva of which
      burrows in apples. Apple flies belong to the genera
      Drosophila and Trypeta.

   Apple midge (Zool.) a small dipterous insect (Sciara
      mali), the larva of which bores in apples.

   Apple of the eye, the pupil.

   Apple of discord, a subject of contention and envy, so
      called from the mythological golden apple, inscribed "For
      the fairest," which was thrown into an assembly of the
      gods by Eris, the goddess of discord. It was contended for
      by Juno, Minerva, and Venus, and was adjudged to the
      latter.

   Apple of love, or Love apple, the tomato (Lycopersicum
      esculentum).

   Apple of Peru, a large coarse herb (Nicandra physaloides)
      bearing pale blue flowers, and a bladderlike fruit
      inclosing a dry berry.

   Apples of Sodom, a fruit described by ancient writers as
      externally of fair appearance but dissolving into smoke
      and ashes when plucked; Dead Sea apples. The name is often
      given to the fruit of Solanum Sodom[ae]um, a prickly
      shrub with fruit not unlike a small yellow tomato.

   Apple sauce, stewed apples. [U. S.]

   Apple snail or Apple shell (Zool.), a fresh-water,
      operculated, spiral shell of the genus Ampullaria.

   Apple tart, a tart containing apples.

   Apple tree, a tree which naturally bears apples. See
      Apple, 2.

   Apple wine, cider.

   Apple worm (Zool.), the larva of a small moth (Carpocapsa
      pomonella) which burrows in the interior of apples. See
      Codling moth.

   Dead Sea Apple.
      (a) pl. Apples of Sodom. Also Fig. "To seek the Dead Sea
          apples of politics." --S. B. Griffin.
      (b) A kind of gallnut coming from Arabia. See Gallnut.
          [1913 Webster]

WordNet (r) 3.0 (2006):

apple tart
    n 1: a small open pie filled with sliced apples and sugar
    2: a tart filled with sliced apples and sugar