Déjà vu is also a very kickass J-Pop song by Dave Rodgers.
Jack: I could have sworn I've been here before. But I know I haven't.
Bob: Heh. Deja vu?
Jack. Yeah. What a strange feeling!
It is an illusion of having already experienced something which in actual fact it is being experienced for the first time.
French : déjà, already + vu, seen