Meaning of zenith line in English:

zenith line

noun

rare
  • 1An arc from the zenith to the horizon, which it intersects at right angles, especially to the point due east on the horizon.

  • 2A straight vertical line between the zenith point at a given location and the centre of the earth.

Origin

Late 16th century; earliest use found in John Blagrave (d. 1611), mathematician.