SG Heritage Dictionary

Zenith [Noun] Webster's Dictionary 1828

That point in the visible celestial hemisphere, which is vertical to the spectator, and from which a direct perpendicular line passing through the spectator, and extended, would proceed to the center of the earth. It is opposed to nadir.

Zenith [Noun] Webster's Dictionary 1913

1. That point in the visible celestial hemisphere which is vertical to the spectator; the point of the heavens directly overhead; -- opposed to nadir.

2. hence, figuratively, the point of culmination; the greatest height; the height of success or prosperity.

Zenithal [Adjective] Webster's Dictionary 1913

Of or pertaining to the zenith.