Meaning

noun (anatomy) a disk of cartilage that serves as a cushion between the ends of bones that meet at a joint

noun (optics) a lens that is concave on one side and convex on the other

noun (physics) the curved upper surface of a nonturbulent liquid in a vertical tube

originEtymology tree Proto-Indo-European *meh₁-? Proto-Indo-European *mḗh₁n̥s Proto-Hellenic *méns Ancient Greek μείς (meís) Proto-Indo-European *-iskos Ancient Greek -ῐ́σκος (-ĭ́skos) Ancient Greek μηνῐ́σκος (mēnĭ́skos) English meniscus From Ancient Greek μηνίσκος (mēnískos, “crescent”), from μήνη (mḗnē, “moon”). Piecewise doublet of moonish.

Etymology from Wiktionary, CC BY-SA 3.0