Meontology is the philosophical study of non-being.
The word comes from the Ancient Greek μή, me "non" and ὄν, on "being" (confer ontology). It refers not exactly to the study of what does not exist, but an attempt to cover what may remain outside of ontology. It can also be associated more recently, with the emphasis placed upon absence or deferral by both Martin Heidegger and Jacques Derrida.
For Emmanuel Levinas, what was meontological was what had meaning beyond being, beyond ontology; for him this was the ethical, the primary demand of the other in the face-to-face encounter. In this sense he sought to clarify or take further some of the issues raised by Heidegger and explicitly give ontology a secondary role to ethics rather than continue to parallel them in saying that the Being means care (German: Sorge).
Nishida was the first to thoroughly expand the Eastern notion of nothingness in the Continental paradigm and is thus responsible for bringing to the West a clearer understanding of the Buddhist notion of non-being.