n. A crescent or crescentshaped body. Specificallyn. A lens, convex on one side and concave on the other, and thicker in the center, so that its section presents the appearance of the moon in its first quarter.n. The convex or concave surface of a liquid, caused by capillarity: thus, the mercury in a barometer has a convex meniscus, but spirit or water a concave meniscus.n. In anatomy, an interarticular fibrocartilage, of a rounded, oval, disklike, or falcate shape, situated between the ends of bones, in the interior of joints, attached by the margins.n. In zoology, a peculiar organ, of doubtful function, found in Echinorhynchus, a genus of acanthocephalous parasitic worms.