Disk /(dĭsk)/

Disk

n.
  1. A discus; a quoit.
    Some whirl the disk, and some the javelin dart.
  2. A flat, circular plate; as, a disk of metal or paper.
  3. The circular figure of a celestial body, as seen projected of the heavens. (Astron.)
  4. A circular structure either in plants or animals; as, a blood disk; germinal disk, etc. (Biol.)
  5. The whole surface of a leaf. (Bot.)
  6. The anterior surface or oral area of cœlenterate animals, as of sea anemones. (Zool.)

Phrases & Compounds
Disk engine
a form of rotary steam engine.
Disk shell
any species of Discina.