Definitions for "Nadir"
That point of the heavens, or lower hemisphere, directly opposite the zenith; the inferior pole of the horizon; the point of the celestial sphere directly under the place where we stand.
The lowest point; the time of greatest depression.
A point on the celestial sphere directly below the observer, diametrically opposite the zenith.
Keywords:  virological, see
See virological nadir.
an important prognostic variable, no absolute value was defined to separate successful from unsuccessful treatments
a strong predictor of ultimate biochemical outcome
Energy web between the realms; mostly disconnected from the Habitat.
Keywords:  straight, sensor, down, remote, sensing
Straight down (toward the center of the Earth).
In remote sensing, refers to a view from a sensor that is looking straight down at the surface.