The Collaborative International Dictionary of English v.0.48:

Disk \Disk\ (d[i^]sk), n. [L. discus, Gr. di`skos. See Dish.]
   [Written also disc.]
   1. A discus; a quoit.
      [1913 Webster]

            Some whirl the disk, and some the javelin dart.
                                                  --Pope.
      [1913 Webster]

   2. A flat, circular plate; as, a disk of metal or paper.
      [1913 Webster]

   3. (Astron.) The circular figure of a celestial body, as seen
      projected of the heavens.
      [1913 Webster]

   4. (Biol.) A circular structure either in plants or animals;
      as, a blood disk; germinal disk, etc.
      [1913 Webster]

   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.
          [1913 Webster]

   6. (Zool.)
      (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.
          [1913 Webster]

   Disk engine, a form of rotary steam engine.

   Disk shell (Zool.), any species of Discina.
      [1913 Webster]

WordNet (r) 3.0 (2006):

disk
    n 1: something with a round shape resembling a flat circular
         plate; "the moon's disk hung in a cloudless sky" [syn:
         disk, disc, saucer]
    2: a flat circular plate [syn: disk, disc]
    3: sound recording consisting of a disk with a continuous
       groove; used to reproduce music by rotating while a
       phonograph needle tracks in the groove [syn: phonograph
       record, phonograph recording, record, disk, 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, disk,
       disc]
    v 1: draw a harrow over (land) [syn: harrow, disk]

Moby Thesaurus II by Grady Ward, 1.0:

92 Moby Thesaurus words for "disk":
   O, annular muscle, annulus, areola, aureole, carousel, chaplet,
   circle, circuit, circumference, circus, closed circle, coat,
   coating, collop, corona, coronet, covering, crown, cut, cycle,
   deal, diadem, discus, eternal return, fairy ring, feuille, film,
   flap, foil, fold, garland, glory, halo, lamella, lamina,
   laminated glass, laminated wood, lap, lasso, leaf, logical circle,
   loop, looplet, magic circle, membrane, merry-go-round, noose,
   orbit, pane, panel, patina, peel, pellicle, plait, plank, plate,
   plating, ply, plywood, radius, rasher, ring, roller, rolling stone,
   rondelle, rotator, rotor, round, roundabout, roundel, rundle,
   safety glass, saucer, scum, sheet, skin, slab, slat, slice,
   sphincter, table, tablet, top, veneer, vicious circle, wafer,
   wheel, whirlabout, whirler, whirligig, wreath



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

DISK
       Deutschsprachige Internationale SAS-benutzer Konferenz


The Free On-line Dictionary of Computing (30 December 2018):

disk
disks

    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)