\Ze"nith\ (?; 277), n. [OE. senyth, OF. cenith, F.
z['e]nith, Sp. zenit, cenit, abbrev. fr. Ar. samt-urras way
of the head, vertical place; samt way, path + al the + ras
head. Cf. {Azimuth}.]
1. That point in the visible celestial hemisphere which is
   vertical to the spectator; the point of the heavens
   directly overhead; -- opposed to {nadir}.
         From morn To noon he fell, from noon to dewy eve, A
         summer's day; and with the setting sun Dropped from
         the zenith, like a falling star.      --Milton.
2. hence, figuratively, the point of culmination; the
   greatest height; the height of success or prosperity.
         I find my zenith doth depend upon A most auspicious
         star.                                 --Shak.
         This dead of midnight is the noon of thought, And
         wisdom mounts her zenith with the stars. --Mrs.
                                               Barbauld.
         It was during those civil troubles . . . this
         aspiring family reached the zenith.   --Macaulay.
{Zenith distance}. (Astron.) See under {Distance}.
{Zenith sector}. (Astron.) See {Sector}, 3.
{Zenith telescope} (Geodesy), a telescope specially designed
   for determining the latitude by means of any two stars
   which pass the meridian about the same time, and at nearly
   equal distances from the zenith, but on opposite sides of
   it. It turns both on a vertical and a horizontal axis, is
   provided with a graduated vertical semicircle, and a level
   for setting it to a given zenith distance, and with a
   micrometer for measuring the difference of the zenith
   distances of the two stars.