A nit in poker is only playing premium starting hands and afraid to put in money without the absolute nuts. Pretty much similar to a rock. In lower stakes games this style is working marginally because the bad players don't pick up on their habit and pay them off anyway. Any decent player can crush them though which is why you generally won't see a nit in higher stakes games.
That guy is a complete nit. He hasn't played a hand for the last hour.