To flicker means to shine or burn unsteadily, with quick changes between brightness and dimness. A candle flame flickers in the breeze, dancing and wavering but never quite going out. The lights might flicker during a thunderstorm when the power wavers for just a moment. Old movies sometimes flicker on screen as the film passes unevenly through the projector.

The word captures something that keeps appearing and disappearing rapidly. You might see a flicker of movement in the corner of your eye, or notice a flicker of worry cross someone's face before they smile. A firefly flickers its light on and off as it flies through a summer evening.

Scientists use flicker to describe anything that pulses or varies quickly: a flickering computer screen, a flickering heartbeat on a monitor, or stars that flicker in the night sky because of shifting air in the atmosphere. The word can suggest something unstable or uncertain, not steady and reliable. When a fire is flickering low, it might be about to go out. When hope flickers, it's still there, but barely.