1 In a novel, film, or other fictional work, a sudden transition to an earlier episode in the narrative.
2 A recurrence of a memory, or the experience of reliving an episode from the past. See also post-traumatic stress disorder.
3 After consumption of a hallucinogen, the re-experiencing of some of the perceptual effects of the intoxication, such as geometric illusions, false perceptions of motion in the periphery of the visual field, flashes of light or colour, afterimages, micropsia, and macropsia. Also called posthallucinogen perception disorder.