Deleuze and Guattari use the term BwO (Body Without Organs) in an extended sense, to refer to the virtual dimension of reality in general (which they more often call "plane of consistency" or "plane of immanence"). In this sense, they speak of a BwO of "the earth." "The Earth," they write, "is a body without organs. This body without organs is permeated by unformed, unstable matters, by flows in all directions, by free intensities or nomadic singularities, by mad or transitory particles" (A Thousand Plateaus, p. 40). That is, we usually think of the world as composed of relatively stable entities ("bodies," beings). But these bodies are really composed of sets of flows moving at various speeds (rocks and mountains as very slow-moving flows; living things as flows of genetic material; language as flows of information, words, etc.). This fluid substratum is what Deleuze calls the BwO in a general sense.
In A Thousand Plateaus, Deleuze and Guattari eventually differentiate between three kinds of BwO: cancerous, empty, and full. Roughly, the empty BwO is the BwO of Anti-Oedipus. This BwO is also described as "catatonic" because it is completely de-organ-ized; all flows pass through it freely, with no stopping, and no directing. Even though any form of desire can be produced on it, the empty BwO is non-productive. The full BwO is the healthy BwO; it is productive, but not petrified in its organ-ization. The cancerous BwO is caught in a pattern of endless reproduction of the self-same pattern.