Plain English Meaning
If you stare at one small light in the dark for long enough, it starts to look like it is moving, even though it is not. Your eyes are creating the illusion because there is nothing else around the light to anchor it.
Full Definition
A visual illusion in which a single, stationary point of light viewed against a dark, featureless background appears to move on its own after being stared at for several seconds. The apparent motion is not real -- it is created by tiny involuntary movements of the eyes when there are no surrounding visual references to fix the light's position.
Context Anchor
Encountered during night flying when looking at isolated lights, stars, or distant ground lights with few other visual references.
Derivation
From Greek 'auto' meaning 'self' and 'kinesis' meaning 'motion' -- literally 'self-motion.' The name describes the illusion exactly: the light appears to move by itself, with no outside cause.
Why Pilots Care
This illusion can pilots to misjudge the position or motion of lights, potentially causing or incorrect decisions during .