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