déjŕ vu The sense of having already experienced an event that is happening at the moment (Fr. "already seen"). This very common phenomenon has never been fully explained, but some scientists believe that a neurological glitch causes the experience to be registered in the memory before reaching consciousness. Other people believe déjŕ vu is an unconscious emotional response triggered by similarities between the current event and a past experience. Frequent occurences of déjŕ vu may be a symptom of temporal lobe epilepsy.

The encyclopedia of the brain and brain disorders - Carol Turkington