Deja vu is the feeling of an event or series of events or happening which aretaking place at that particular moment might have already taken place sometime back.A feeling which makes a person feel that he/she is experiencing the event or thought again.
The sensation of feeling like something has happened before. For example, say one day you saw a man in a red jacket at the store in isle 17. A few weeks later, you see the same man in the same jacket in the same isle. You might say, "deja vu'."