Hallucination Perception life experience with the clarity and impact of a true perception but without the external stimulation of the relevant sensory organ. This should be distinguished from Illusions and which an actual external stimulus is misperceived or misinterpreted. The person may or may not have insight into the non-veridical nature of these perceptions. Copyright Notice Adapted from Wikipedia. Text is available under the  Creative Commons Attribution-ShareAlike License 3.0 ; additional terms may apply.