1. A thin, flat, circular object or plate. 2. The moon's disk was reflected in the pond. 3. The disk used in a disc brake. 4. A disk used on a disk harrow. 5. A round, flattened, platelike structure in an animal, such as an intervertebral disk. 6. discus 7. A phonograph record. 8. An optical disk, especially a compact disk. 9. A magnetic disk. 10. A circular grid in a phototypesetting machine. 11. To work (soil) with a disk harrow. 12. To make (a recording) on a phonograph record.