noun. 
                    In classical antiquity, a circular piece of stone or plate of metal, about 12 inches in diameter, pitched from a fixed point to the greatest possible distance, as a gymnastic exercise and as an athletic contest.
                  
                
                  
                    noun. 
                    In anatomy, physical, zoology, and botany, a disk of any kind.
                  
                
                  
                    noun. 
                    [capitalized] In zoöl.: A genus of mollusks, A genus of acalephs.
                  
                
                  
                    noun. 
                    A genus of scombroid fishes.