• (n.) The impression of a vivid sensation retained by the retina of the eye after the cause has been removed; also extended to impressions left of tones, smells, etc.
an unwanted image reappearing after the apparent removal of the charge corresponding to a previously stationary image
Aft'er-im`age noun The impression of a vivid sensation retained by the retina of the eye after the cause has been removed; also extended to impressions left of tones, smells, etc. 
The illusion of a visual complementary color image that occurs after staring at a hue, then shifting the gaze to a plain white surface.
An image seen after the eye's retina has been exposed for a time to an intense or stationary light source. It may be negative or positive, or appear in complementary colours.