1) Concave 2) Concave on both sides 3) Concavo-concave 1) Concave 
• (a.) Concave on both sides; as, biconcave vertebrae.
(bi″kon-kāv´) having two concave surfaces.
Bi·con'cave adjective [ Prefix bi- + concave .] Concave on both sides; as, biconcave vertebræ. 
Type: Term Pronunciation: bī-kon′kāv Definitions: 1. Concave on two sides; denoting especially a form of lens. Synonyms: concavoconcave
[adj] - concave on both sides
biconcave 1. Concave on both sides; as, a biconcave vertebrae or as a lens. 2. A description of a lens with two faces that are concave
concavo-concave adjective concave on both sides
concave on both sides, as a lens. See diag. under