Source : Webster's Revised Unabridged Dictionary (1913)

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.

Source : WordNet®

hypethral
     adj : partly or entirely open to the sky [syn: {hypaethral}]