Meniscus

Zell's Condensed Dictionary · 1879 · p. 30

(me-nis'küs.) [From Gr. mēniskos, a half moon. (Opt.) A lens, convex on one side, and concave on the other, and on which the two surfaces would meet if continued-wherein it differs from a concavoconvex lens, in which the two surfaces would not meet if continued. [s. 592]