What is 'Database Mining'

I feel sure I have heard the phrase "database mining" here and there. Can someone tell me what it is? I find myself doing something that feels a lot like database mining (dirty, dangerous, exhausting, environmentally questionable) in that I am searching through large, non-normalised tables, trying to uncover structure in the underlying data. I find myself wanting to "factor" a large table into two smaller tables - basically "unjoin" it. If there is a theory or a method behind this, I'd love to get a pointer to it. Paul PS As you can see, I don't exactly know what I am talking about, but I am hping it strikes a chord with someone out there.