We find the following description on the fascinating website of the International Association For Near-Death Studies (IANDS):
A near-death experience (NDE) is a profound psychological event that may occur to a person close to death or, if not near death, in a situation of physical or emotional crisis. Because it includes transcendental and mystical elements, an NDE is a powerful event of consciousness; it is not mental illness.
Whether happening “truly near death” or under benign circumstances, the near-death experience contains powerful images and emotions, usually of peace and love though sometimes terror, despair, guilt. An NDE may include an out-of-body experience and vivid perceptions of movement, light, darkness; encounters with deceased loved ones, unfamiliar entities and/or spiritual presences; sometimes a life review, a landscape, a sense of overpowering knowledge and purpose. The aftereffects of an NDE or related experience are enduring, often powerful, and may be life-altering.
The NDE belongs to a larger family of experiences that go beyond the usual limits of space and time and can transform a person's life and beliefs. They may be called spiritually transformative, conversion, mystical, religious, or transpersonal experiences.