The Collaborative International Dictionary
Opisthocoelous
Opisthocoelian \O*pis`tho*c[oe]"li*an\, Opisthocoelous \O*pis`tho*c[oe]"lous\, a. [Gr. 'o`pisqen behind + koi^los hollow,] (Anat.) Concave behind; -- applied especially to vertebr[ae] in which the anterior end of the centrum is convex and the posterior concave.
Wiktionary
opisthocoelous
a. concave behind; applied especially to vertebrae in which the anterior end of the centrum is convex and the posterior concave