The Collaborative International Dictionary of English v.0.48:

Lenticular \Len*tic"u*lar\ (-l[~e]r), a. [L. lenticularis: cf.
   F. lenticulaire. See Lenticel.]
   Resembling a lentil in size or form; having the form of a
   double-convex lens.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lenticular
    adj 1: convex on both sides; shaped like a lentil [syn:
           biconvex, convexo-convex, lenticular, lentiform]