Source : Webster's Revised Unabridged Dictionary (1913)

Disk \Disk\, n. [L. discus, Gr. ?. See {Dish}.] [Written also
   {disc}.]
   1. A discus; a quoit.

            Some whirl the disk, and some the javelin dart.
                                                  --Pope.

   2. A flat, circular plate; as, a disk of metal or paper.

   3. (Astron.) The circular figure of a celestial body, as seen
      projected of the heavens.

   4. (Biol.) A circular structure either in plants or animals;
      as, a blood disk; germinal disk, etc.

   5. (Bot.)
      (a) The whole surface of a leaf.
      (b) The central part of a radiate compound flower, as in
          sunflower.
      (c) A part of the receptacle enlarged or expanded under,
          or around, or even on top of, the pistil.

   6. (Zo["o]l.)
      (a) The anterior surface or oral area of c[oe]lenterate
          animals, as of sea anemones.
      (b) The lower side of the body of some invertebrates,
          especially when used for locomotion, when it is often
          called a creeping disk.
      (c) In owls, the space around the eyes.

   {Disk engine}, a form of rotary steam engine.

   {Disk shell} (Zo["o]l.), any species of Discina.

Source : WordNet®

disk
     v : draw a harrow over (land) [syn: {harrow}]

disk
     n 1: something with a round shape like a flat circular plate
          [syn: {disc}, {saucer}]
     2: a flat circular plate [syn: {disc}]
     3: sound recording consisting of a disc with continuous
        grooves; formerly used to reproduce music by rotating
        while a phonograph needle tracked in the grooves [syn: {phonograph
        record}, {phonograph recording}, {record}, {disc}, {platter}]
     4: (computer science) a memory device consisting of a flat disk
        covered with a magnetic coating on which information is
        stored [syn: {magnetic disk}, {magnetic disc}, {disc}]

Source : Free On-Line Dictionary of Computing

disk
     
         1. {magnetic disk}.
     
        2. {compact disc}.
     
        3. {optical disk}.
     
        Note: the american spelling, "disk", is normal for most
        computer disks whereas "compact disc", having come to
        computers via the audio world, is correctly spelled with a
        "c", indeed, this spelling is part of the CD standard.
     
        (1995-07-30)