when one senses a feeling of reoccurance. when there is a feeling that you have already seen the whole scenario or scene that is surrounding you. sometimes these deja vu's occur in dreams. one may dream of something that at the time makes no sense but days, weeks, or months later, it happens and it all of a sudden hits you.
oh my goodness that's really freaky, i just had a deja vu. months ago i think of dreamt of exactly what just happened. she was wearing that, he replied to her comment and the same music was playing in the background