What is "disk engine"

Disk \Disk\ (d[i^]sk), n. [L. discus, Gr. di`skos. See Dish.]

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.)

   1. The whole surface of a leaf.

   2. The central part of a radiate compound flower, as in sunflower.

   3. A part of the receptacle enlarged or expanded under, or around, or even on top of, the pistil.

6. (Zo["o]l.)

   1. The anterior surface or oral area of c[oe]lenterate animals, as of sea anemones.

   2. The lower side of the body of some invertebrates, especially when used for locomotion, when it is often called a creeping disk.

   3. In owls, the space around the eyes.

      Disk engine, a form of rotary steam engine.

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