A momentary bright shimmer of reflected light, generally diamond- or star-shaped, and short-lived. Groups of them tend to appear and vanish in various instances.
Sparkle, glint, and diffraction spikes all refer to similar patterns of bright lines radiating from a point. They are not clearly differentiated, and usage tends to be context-sensitive. In general:
Sparkle is considered the base case. Usually four lines at right angles radiating from a point. Associated with eyes, liquid or particulate matter (e.g. raindrops, snow, sand), or nothing (appearing mid-air). Can appear in large numbers.
Glint is associated with solid objects, especially ones which are metallic and/or sharp. Usually appear singly or in small numbers.
Diffraction spikes is the technical term for the phenomenon in general, but is used less often. Can be used for more realistic-looking effects or conversely when appearing extremely large and exaggerated. More likely than sparkle and glint to be asymmetric or to have more than four radiating lines.
See also
sparkling aura for multiple sparkles around a certain object or character.
