Noun
That point in the visible celestial hemisphere which is vertical to the spectator; the point of the heavens directly overhead; -- opposed to nadir.
hence, figuratively, the point of culmination; the greatest height; the height of success or prosperity.
Source: Webster's dictionaryAmerican power worldwide is at its historic zenith. Zbigniew Brzezinski
Madness blew so violently on the immeasurable air pump of the circuit, that it took the form of a spiral, rising like a screw to the Zenith.. [describing the Brescia automobile races, in 1907]. Filippo Tommaso Marinetti
This dead of midnight is the noon of thought, And Wisdom mounts her zenith with the stars. Anna Letitia Barbauld
I think one of the reasons people quit is because they're afraid they won't be able to get better and better; that they have to come to a zenith of some kind. Conrad Hall
The towers of Zenith aspired above the morning mist; austere towers of steel and cement and limestone, sturdy as cliffs and delicate as silver rods. Sinclair Lewis
An immense and regular ugliness reigned within it. The country enjoyed perfect tranquillity. It had reached its zenith. Anatole France