Shinobi, man, a deja vu is when you feel like what you're experiencing at the moment has already happened, or you dreamed it. It's french for "already seen". I think. And as for MC's theory, I don't think you're right, since I can clearly predict what is going to happen next, and the signals from my eyes to my brain are definitely not slow, cause that would mean like "WATCH OUT THERE'S A BALL COMING AT UR HEAD! WTF!?!?! I DON'T SEE IT, BUT HEY, IT'S DEJA VU!!" I definitely think it's happening because humans don't have a good enough understanding of the fourth dimension. That is, time. Think of it this way: We are all on a piece of paper. We are all 2-dimensional. One of us gets sent to jail. It has four walls, that are just lines. But since we're 2-dimensional, those seem like walls to us. BUT, if someone that is 3-dimenisonal could pick us up from that piece of paper from UP, that would look to us as if the hand of that somebody is passing through the ceiling, or wall. But when it comes to being 4-dimensional, that's something we can't comprehend, but the brain can. That's why we get Deja Vu. We're all 4-dimensional, since we exist in TIME. But we can't move through all 4 dimensions, at least not yet. Or maybe, not consciously. Maybe we do indeed move through 4 dimensions when we SLEEP. That could explain why we think we dreamed the Deja Vu. It all seems very made-up and ridicilous, but that's just how I think. Like this:
People ask me why I don't believe in God. I say because I have never seen, heard or felt him. They ask: "Then who created the universe?" I say: Nothing. Nothing created the universe. They ask: "How is that possible?" I say: "Well, we know that the universe is EVERYTHING, and that there's nothing beyond it. But a thing can't create itself, therefore everything can't create everything. Therefore, EVERYTHING had to be created by something that ISN'T everything. And that is...nothing. And if something did indeed create the universe, then it existed before the universe, and since the universe and that which created it are everything, and that which created it came before the universe, before the universe was created that which created the universe was EVERYTHING. And again, everything can't create everything, so everything must've been created by something that isn't everything, and taht is..nothing."
EDIT: I'd trust myself before Wikipedia, shinobi. A Deja Vu can't be studied nor controlled, so there's absolutely no way we can determine what it really is. All we can do is THINK what it is.