What does it mean if you dream of deja vu?

There's no one explanation for frequent episodes of deja vu. Could be a recurrence of dreams not remembered consciously. Could be an event of dreams of the future. Could be recurrences of events when we were too young to remember them consciously. Or, it could be recurrences of happenings in an earlier lifetime which are impossible to remember, except perhaps through expert hypnotism with regression.