A glitter is a sparkle or flash of light. To glitter is to gleam or shine, as if glistening with moisture.
Glitter isn’t just shiny stuff you use in craft projects. When used as a noun, glitter can refer to any kind of gleam, glint, spark, or flash of light, like the flicker of a firefly at night. This word can also be used as a verb. An ornate golden goblet glitters brightly — as does anything coated in a thick layer of glitter.