(n.) A circular structure either in plants or animals; as, a blood disk; germinal disk, etc.
(n.) A discus; a quoit.
(n.) A flat, circular plate; as, a disk of metal or paper.
(n.) A part of the receptacle enlarged or expanded under, or around, or even on top of, the pistil.
(n.) In owls, the space around the eyes.
(n.) The anterior surface or oral area of coelenterate animals, as of sea anemones.
(n.) The central part of a radiate compound flower, as in sunflower.
(n.) The circular figure of a celestial body, as seen projected of the heavens.
(n.) The lower side of the body of some invertebrates, especially when used for locomotion, when it is often called a creeping disk.
(n.) The whole surface of a leaf.