meniscus

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A crescent-shaped body.
2. n. A concavo-convex lens.
3. n. The curved upper surface of a nonturbulent liquid in a container that is concave if the liquid wets the container walls and convex if it does not.
4. n. A cartilage disk that acts as a cushion between the ends of bones that meet in a joint.

Century Dictionary and Cyclopedia

1. n. A crescent or crescentshaped body. Specifically
2. n. 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. As the convexity exceeds the concavity, a meniscus may be regarded as a convex lens (also called a converging meniscus); the corresponding form in which the convexity is less than the concavity is sometimes but improperly called a diverging meniscus. See cut under lens.
3. 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.
4. 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. Such cartilages are found in man in the tem-poromaxillary, the sternoclavicular, and sometimes the acromioclavicular articulations, and in the wrist- and knee-joints.
5. n. In zoology, a peculiar organ, of doubtful function, found in Echinorhynchus, a genus of acanthocephalous parasitic worms.

Wiktionary

1. n. A crescent moon, or an object shaped like it. [from 17th c.]
2. n. A lens which is convex on one side and concave on the other, being crescent-shaped in cross-section. [from 17th c.]
3. n. The curved surface of liquids in tubes, whether concave or convex, caused by the surface tension of the liquid. [from 19th c.]
4. n. Either of two parts of the human knee that provide structural integrity to the knee when it undergoes tension and torsion. [from 19th c.]

GNU Webster's 1913

1. n. A crescent.
2. n. A lens convex on one side and concave on the other.
3. n. An interarticular synovial cartilage or membrane; esp., one of the intervertebral synovial disks in some parts of the vertebral column of birds.

WordNet 3.0

1. n. (anatomy) a disk of cartilage that serves as a cushion between the ends of bones that meet at a joint
2. n. (optics) a lens that is concave on one side and convex on the other
3. n. (physics) the curved upper surface of a nonturbulent liquid in a vertical tube