concavo-concave

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Concave on both surfaces; biconcave. Used of a lens.

from The Century Dictionary.

• Concave or hollow on both surfaces, as a lens. Lenses of this kind are more frequently termed double-concave lenses. See lens.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Concave or hollow on both sides; double concave.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective concave on both sides