n.

1. 【天】天頂[the S]
   zenith telescope

   天頂儀

   It felt as if we had traveled from nadir to zenith.

   感覺上我們好像已從天底走到了天頂。

2. 最高點；頂點；極盛時期[S1]
   Michael felt that he had already passed the zenith of his power.

   麥克覺得自己的權力已過了頂盛期。

   Being elected class president was the zenith of my years in high school.

   當選級長是我中學時代最輝煌的時刻。

n.

1. the time at which something is most powerful or successful.
2. the point in the sky directly overhead. The opposite of nadir.
   ▸the highest point in the sky reached by a given celestial object.