What is a "publishable" thesis? What is a "publishable" thesis?

I have often heard this term thrown about in conferences and even as advice to new grad. students.

From what I know, it is indeed rare for a thesis to be published entirely as a book, though one can publish papers out of the thesis.
In some cases it might mean that the thesis could be published as a book. However, I'd generally interpret the phrase to mean that the thesis could readily be adapted and published as one or more journal articles.