What is the X in X-mas?
"crescent-shaped body," 1690s in reference to lenses, c.1812 in reference to liquid surfaces, Modern Latin meniscus, from Greek meniskos "lunar crescent," diminutive of mene "moon" (see moon (n.)). Related: Meniscoid.
meniscus me·nis·cus (mə-nĭs'kəs)
n. pl. me·nis·cus·es or me·nis·ci (-nĭs'ī, -kī, -kē)
A crescent-shaped body.
A concavo-convex lens.
The curved upper surface of a nonturbulent liquid in a container that is concave if the liquid wets the walls and convex if it does not.
A disk of cartilage that acts as a cushion between the ends of bones in a joint.
Plural menisci (mə-nĭs'ī, -kī, -kē) or meniscuses