What is "hypethral"

Hypaethral \Hy*p[ae]"thral\, Hypethral \Hy*pe"thral\, a. [L. hypaethrus in the open air, uncovered, Gr. ?; ? under + ? ether, the clear sky.] (Arch.) Exposed to the air; wanting a roof; -- applied to a building or part of a building.
--Gwilt.

a. (alternative form of hypaethral English)

adj. partly or entirely open to the sky [syn: hypaethral]