Déjà vu-The illusion of having already experienced something actually being experienced for the first time.
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déjÃ* vu: Definition from Answers.com
that is the technical definition. however scientist haven't yet found a good explanation for it. i believe our minds are wired so well that we know what is going to happen next. basically our minds have built in instincts that help us realize what is happening then we subconsciously layer the current event with another one just like it.
that sounds oddly painful right.