dip·lo·e or dip·lo·ë 
(dĭplō-ē′)
(dĭplō-ē′)n.
The spongy, porous, bony tissue between the hard outer and inner bone layers of the cranium.
[Greek diploē, a fold, doubling, from feminine of diploos, twofold; see dwo- in the Appendix of Indo-European roots.]
diplo·ic (-lō-ĭk) adj.