Plain English Meaning
The way your eyes see when it is very dark. You see shapes and movement in shades of gray, and things appear clearer when you look slightly to the side of them rather than straight at them.
Full Definition
Vision in low-light conditions that relies on the rod cells of the retina rather than the cone cells. Rods are highly sensitive to dim light but do not detect color and have a blind spot at the center of the visual field, so scotopic vision produces images that are gray-toned and best perceived slightly off-center.
Context Anchor
Seen in night flying and night vision training, especially when learning why pilots look slightly to one side of a dim object instead of staring directly at it.