1. Temporary loss of consciousness due to decreased blood flow to the brain.
2. Momentary loss of consciousness as an absence.
3. Temporary loss of vision, without alteration of consciousness, due to positive (normal) g (gravity) forces; caused by temporary decreased blood flow in the central retinal artery, and seen mostly in aviators.
4. A transient episode that occurs during a state of intense intoxication (alcoholic blackout) for which the person has no recall, although not unconscious (as observed by others).