Frisbee, e.g. (4)
(Other definitions for disc that I've seen before include "Flat round plate" , "Body without limbs" , "Forty-five" , "Layer of cartilage between spinal vertebrae" , "In Olympic event" .)
(Other definitions for disk that I've seen before include "Thin, flat, circular plate" , "Floppy - - (comput.)" .)