bi·con·cave 
(bī′kŏn-kāv, bī-kŏnkāv′)
(bī′kŏn-kāv, bī-kŏnkāv′)adj.
Concave on both sides or surfaces: a biconcave lens.
bi′con·cavi·ty (-kăvĭ-tē) n.
biconcavebiconcave (left) and biconvex (right) lenses
- crosshead
- cross-index
- crossing
- crossing over
- crossing-over
- cross-legged
- cross-link
- crossly
- cross matching
- cross mind
- cross multiplication
- cross-multiply
- cross-national
- crossness
- cross (one's) mind
- cross one's mind
- cross (one's) t's
- cross one's t's
- crossopterygian
- cross over
- crossover
- cross palm
- crosspatch
- crosspiece
- cross-pollinate