Noun

(en noun)

A particular period of history, especially one considered remarkable or noteworthy.

*{{quote-magazine, date=2012-01

, author=Donald Worster , title=A Drier and Hotter Future , volume=100, issue=1, page=70 , magazine= citation , passage=Phoenix and Lubbock are both caught in severe drought, and it is going to get much worse. We may see many such [dust] storms in the decades ahead, along with species extinctions, radical disturbance of ecosystems, and intensified social conflict over land and water. Welcome to the Anthropocene, the epoch when humans have become a major geological and climatic force.}}

A notable event which marks the beginning of such a period.

(astronomy) A precise instant of time that is used as a reference point.

(computing, uncountable) A precise instant of time that is used as a reference point (e.g. January 1, 1970, 00:00:00 UTC).

Noun

(en noun)

(astronomy) The point in the sky vertically above a given position or observer; the point in the celestial sphere opposite the nadir.

* 1638 Herbert, Sir Thomas Some years travels into divers parts of Asia and Afrique

The 12 day wee had the wind high and large ?o that in two dayes ?aile we made the Sunne our Zenith or verticall point...

* 1671–1693 : Rev. Thomas Jolly, private notebook ; printed in:

* 1895 , Henry Fishwick (editor), The Note Book of the Rev. Thomas Jolly: A.D. 1671–1693. Extracts from the Church Books of Altham and Wymondhouses, 1649–1725. And an Account of the Jolly Family of Standish, Gorton, and Altham , page 44

In this 10th m. appeared that prodigious Comett the tayl whereof was like the blade of a double edged sword, and reached almost from the horizon to the zenith .

(astronomy) The highest point in the sky reached by a celestial body.

* 1719-

...in the middle of the day, when the sun was in the zenith , the violence of the heat was too great to stir out...

* 1920 , , The Understanding Heart , Chapter II:

As far to the west as Monica could see, her world was a sea of fog, , the fog gradually took on a bluish tinge.

Highest point or state; peak.

* Shakespeare

I find my zenith doth depend upon / A most auspicious star.

* Macaulay

It was during those civil troubles this aspiring family reached the zenith .

* {{quote-book

, page=173 , year=1900 , author=William Beckford , title=The History of the Caliph Vathek citation , passage="There for a while I enjoyed myself in the zenith of glory and pleasure."}}