1. upper surface of liquid: the curved upper surface of a still liquid in a tube, concave if the liquid wets the walls of the container, convex if it does not, caused by surface tension
2. cartilage disk: a crescent-shaped cartilage disk cushioning the end of a bone where it meets another bone in a joint, especially in the knee
3. concavo-convex lens: a lens that is convex on one side and concave on the other
4. crescent shape: a crescent-shaped body or figure
[Late 17th century. Via modern Latin< Greek mēniskos "little moon" < mēnē "moon"]
