Meniscus \Me*nis"cus\, n.; pl. L. {Menisci} (-s[imac]), E. {Meniscuses}. [NL., from Gr. mhni`skos, dim. of mh`nh the moon.] 1. A crescent. [1913 Webster] 2. (Opt.) A lens convex on one side and concave on the other. [1913 Webster] 3. (Anat.) An interarticular synovial cartilage or membrane; esp., one of the intervertebral synovial disks in some parts of the vertebral column of birds. [1913 Webster] {Converging meniscus}, {Diverging meniscus}. See {Lens}. [1913 Webster]