Butler's writing is overly complex because it's a smokescreen. Many of us were reminded to watch out for this particular smokescreen by the Sokal hoax, but not all. Godel's incompleteness theorem can be stated simply despite its far-reaching implications. So can Butler's point, but if she states it simply it will not be meaningful.
The scientific, biological definition of gender is robust, consistent and predictive. I can tell you with great accuracy that an egg fertilized by a sperm with a Y chromosome will produce a male and not a female. I can tell you that this sexual dimorphism has been reproduced over millions of years and trillions of iterations with no tendency towards collapsing into a continuum. I can tell you there is no reasonable basis to doubt that it will remain stable for the foreseeable future.
What of the social definition of gender? Well, first somebody would have to put forward a social definition of gender and, of course, once they did we would immediately find that it was neither robust nor consistent and certainly not predictive. We would find no precedent in Nature and no consistent pattern across social history, let alone evolutionary history. We would, of course, start with the scientific definition of sexual dimorphism because even a philosopher can't avoid the facts. Then we would try and find sub-groupings of these two sceintific genders by using this and that social trapping to define them. These sub-groupings would not prove consistent. Any attempt to define a "middle" gender would run into the fact that the dimorphism is stable and the "middle" grouping is not - the result of biological accident and/or deliberate attempts to reproduce the outward appearance of one of the scientific genders.
And what of Butler's point? It is true that all definitions and systems of analysis are incomplete. Godel proves this with more subtlety and finality than any philosopher. He posits a machine which only tells the truth and proves that even such a machine can be foiled. This renders the truth that all definitions and systems are incomplete into a truism, for all but the most subtle, mathematical inquiries. In other words, while it is true that all definitions and systems are incomplete, it is not important in many cases because there are definitions and systems so robust that the likelihood they will ever need to be re-examined is miniscule to the point that such a likelihood can safely be ignored.
Butler, like many social philosophers, has tried to inflate the inevitable - but often meaningless - fact that all definitions are the product of mind into a significant, meaningful uncertainty. Except that she does not prove that the uncertainty is meaningful or significant, only that it exists and that we already know. Butler may make significant and meaningful social observations, but her attempt to make an ontological point fails. Subjectivity is a given. One must prove that there is a significant likelihood that a subjective definition will depart meaningfully from objective truth before one has established doubt in that definition.
Nobody in this discussion has offered anything to establish doubt that the definition of two genders, reflecting millions of years of self-perpetuating sexual dimorphism, is a meaningful, robust, consistent and predictive one. Moreover, nobody has put forward a definition of gender that is more robust than the biological one. Unless serious doubt is raised and a serious alternative definition is put forward, the doubt expressed here about the biological definition of gender will be very similar to the doubt expressed by creationists about evolution - conjecture without substance.
boddi