Concavo-convex
Pronunciation : Con*ca`vo-con"vex
Part of Speech : a.
Definition : 1. Concave on one side and convex on the other, as an eggshell or a crescent.
2. (Optics)
Defn: Specifically, having such a combination of concave and convex sides as makes the focal axis the shortest line between them. See Illust. under Lens.
Source : Webster's Unabridged Dictionary, 1913