A writing question? The E book

When is a book published?
In the rareified atmosphere of publishing a book is only deemed to be "published" when it can be held in your hand.
But what of E books. They are becoming popular. They are cheap. So are they published in the real world, even if they are self published.
I think anything that is out there in the public arena can be considered published, even without the backing of a 'house'.