The Collaborative International Dictionary of English v.0.48:

Concavo-convex \Con*ca`vo-con"vex\, a.
   1. Concave on one side and convex on the other, as an
      eggshell or a crescent.
      [1913 Webster]

   2. (Optics) Specifically, having such a combination of
      concave and convex sides as makes the focal axis the
      shortest line between them. See Illust. under Lens.
      [1913 Webster]

WordNet (r) 3.0 (2006):

concavo-convex
    adj 1: concave on one side and convex on the other with the
           concavity being greater than the convexity