The Collaborative International Dictionary of English v.0.48:

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.
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   2. (Opt.) A lens convex on one side and concave on the other.
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   3. (Anat.) An interarticular synovial cartilage or membrane;
      esp., one of the intervertebral synovial disks in some
      parts of the vertebral column of birds.
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   Converging meniscus, Diverging meniscus. See Lens.
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