Fr.: arc circumzénithal
A colorful halo centered on the zenith, appearing when the solar elevation above the horizon is not too high (< 32°).
Of or relating to the → zenith; located at or near the zenith.
Fr.: puits zénithal
1) A well used in Antiquity from bottom of which the sky could be observed
during the day with a better contrast. The aperture of the well reduced the
light diffused by the sky.