noun

• A crescent moon, or an object shaped like it.
• (optics) A lens which is convex on one side and concave on the other, being crescent-shaped in cross-section.
• The curved surface of liquids in tubes, whether concave or convex, caused by the surface tension of the liquid.
• (anatomy) Either of two parts of the human knee that provide structural integrity to the knee when it undergoes tension and torsion.