APA Dictionary of Psychology

perceptual experience that does not accurately represent external reality or stimuli, but instead is a distorted perception of a real stimulus (e.g., illusions, perceptual errors) or a perception without an external stimulus (e.g., hallucinations). Non-veridical perception can be a result of cognitive biases, expectations, fatigue, substance use, or neurological conditions. Compare to veridical perception. See also perceptual distortion.