• WordNet 3.6
    • adj hypethral partly or entirely open to the sky
    • ***
Webster's Revised Unabridged Dictionary
    • a Hypethral (Arch) Exposed to the air; wanting a roof; -- applied to a building or part of a building.
    • ***
Century Dictionary and Cyclopedia
    • hypethral Open to the sky; roofless; not covered in; in the open air, as a court, inclosure, or place.
    • hypethral In architecture hypethral is specifically applied to a supposed ancient type of building lighted by the omission of a large section of the roof. This notion is based upon interpretations of Vitruvius and the negative evidence afforded until now by the lack of remains explaining methods of lighting among the ruins of Greek temples. It is certain, however, that no Greek temple with its contained art treasures was ever intentionally exposed in this way to the weather. The temples called hypethral by Greek writers were roofless either from accident or from being unfinished. In the smaller Greek temples it is probable that daylight was admitted only by the door, and that it was supplemented by artificial light. In large temples, such as the Parthenon at Athens, of which the cella interior was 100 feet long, it is improbable that the lighting was wholly artificial; but no satisfactory explanation has yet been given of its management. It has been conjectured that such interiors were lighted by a system of narrow open channels in the roof, over the side aisles, or by series of apertures in the roof serving as windows, and capable of being closed. There was no break in the ridge-line of the root, and no superstructure or clearstory rising above the roof. See cut under temple.
    • ***


Webster's Revised Unabridged Dictionary
L. hypaethrus, in the open air, uncovered, Gr. ; under + ether, the clear sky


In poetry:

And he, so serene, so majestic, so true,
Whose temple hypethral the planets shine through,
Let us catch but five words from that mystical pen,
We should know our one sage from all children of men.
"For Whittier’s Seventieth Birthday" by Oliver Wendell Holmes