Nothingness, not even a noun. The word itself cannot be classified because it refers to nothing in itself. It is at it's closest with being an abstract noun, because it mentions an idea and though few people know it, a noun is a: person, place, thing OR IDEA. Below is the Wikipedia defined term of nothing:
Nothing is the lack or absence of anything at all. Colloquially, the term is often used to indicate the lack of anything relevant or significant, or to describe a particularly unimpressive thing, event, or object.

And here is the article which is an excerpt from wiki:

"Logic and philosophy

Grammatically, the word "nothing" is a noun, which suggests that it refers to some thing. This can lead to confusion and forms the basis for a number of jokes. Its basic uses can often be restated to avoid this appearance: "There is nothing in the basement" can be restated as "There is not anything in the basement" or "Everything is not in the basement." "Nothing is missing" can be restated as "everything is present". Conversely, many fallacious conclusions follow from treating "nothing" as a noun. In one old joke, if nothing is worse than the Devil, and nothing is greater than God, then the Devil must be greater than God:

(nothing) > God \wedge Devil > (nothing)

\to Devil > (nothing) > God

\to Devil > God

Modern logic made it possible to articulate these points coherently as intended, and many philosophers hold that the word "nothing" does not function as a noun: there is not any object it refers to. There are still various opposing views, though: that, for example, our understanding of the world rests essentially on noticing absences and lacks as well as presences, and that "nothing" and related words serve to indicate these.

The concept of 'nothing' has been studied throughout history by philosophers and theologians; many have found that careful consideration of the notion can easily lead to the logical fallacy of reification. (If one does not believe that nothing is no thing.) The understanding of 'nothing' varies widely between cultures, especially between Western and Eastern cultures and philosophical traditions. For instance, Shunyata (emptiness), unlike "nothingness," is considered a state of mind in Buddhism (see Nirvana, mu, and Bodhi). Existentialism and Martin Heidegger have brought these two understandings closer together.

[edit] Science

In mathematics, nothing does not have a technical meaning. It could be said that a set contains "nothing" if and only if it is the empty set, in which case its cardinality (or size) is zero. In other words, the word "nothing" is an informal term for an empty set.

In physics, the word nothing is not used in any technical sense. A region of space is called a vacuum if it does not contain any matter. But it can contain physical fields. In fact, it is practically impossible to construct a region of space which contains no matter or fields, since gravity cannot be blocked and all objects at a non-zero temperature radiate electromagnetically. However, supposing such a region existed, it would still not be "nothing", since it has properties and a measurable existence as part of the quantum-mechanical vacuum.

In computing, "Nothing" (VB.Net), or "null" (Java, C#, [others), can be a keyword used to represent an unassigned variable, or a pointer that does not point to any particular memory address, or a reference that does not refer to an extant object. Similarly, Null is used in SQL as a symbolic representation of the absence of data. This meta-data usage of "null" is different from the unprintable ASCII and unicode null character, which has a numerical value of zero — although it is different from the ASCII character for zero ("0"). The ASCII blank character (" ") is not the same as an empty string (""), which is itself sometimes confused with the null pointer in languages such as C. Most forms of assembly language have a no-operation (nop) instruction (often with a numerical value of zero) — that is, a command to do nothing, which can prove useful for blanking out areas of problem code."

With ALL of that said, I have "nothing" left to say. Other than, of course, what does it essentially matter? I mean, sure it seems interesting on the OUTSIDE but if you truly look at the whole picture, what does it matter if you think nothing is something or not? It IS a very disturbing theological topic and I wouldn't mind discussing it, however, it is late and I really just like the word itself. With that said, do this for me, I want YOU to imagine what "NOTHING", and I mean nothing, not blank, looks like. You can't. However if such a place in space were to exist, and it was nothing, it would still be SOMETHING!!!!