Well, I don't like stupid names like "Joe Sixpack", "Joe Average", or whatever. The average 'idiot' user is someone who will characteristically describe themselves as an 'idiot with computers'. They don't know what a kernel is, they frequently think that 3.5" floppy disks are 'hard disks', they don't know what the 'internet' is (although they know how to check and send email), and they don't know a whole lot of things. Windows has abstracted most things so that people don't *have* to know about computers to use them. This is bad, but is a subject for another article entirely.
So, your average 'idiot' user isn't necessarily an idiot, they just don't know much about computers. They can point to a mouse, use it to point and click, and probably don't even know how to touchtype. They know that if their computer breaks, reboot it. If that doesn't fix it, call someone who knows more than they do. You might be an average 'idiot' user. You might be the person the average 'idiot' user calls to fix their computer.