Apple took to the offensive this week in its bid to convince the courts to toss aside Microsoft's complaint that Apple's attempt to trademark the term "App Store" was invalid. Apple claims instead that the term is no more generic or less protectable a trademark as "Windows," a term for which Microsoft holds its own oft-debated trademark.

"Microsoft falls far short of proving by clear and convincing evidence that a majority of the relevant public uses the term App Store generically for any online software marketplace," a 63-page Apple filing reads. "Further, Microsoft acknowledges that Apple's principal competitors have all found ways of competing with Apple by offering online software marketplace services of their own without using the term App Store."

Amusingly, Apple doesn't just rely on its admittedly rigorous legal defense to sway the decision makers at the US Patent and Trademark Office (USPTO). The company has also enlisted the help of a linguistics expert, Dr. Robert Leonard, who, the company says, "concludes that 'the predominant usage of the term App Store is as a proper noun to refer to Apple's online application marketplace'."

"Accordingly, Microsoft's motion should be denied," the introductory section of the filing concludes.

Microsoft first complained about Apple's App Store trademark filing in January, arguing that the term is generic, has been used by many companies, and should be open to competitors. This argument caused the USPTO appeals board to mark Apple's claim—which dates back to 2008—as "pending." Microsoft is seeking a summary judgment.

In Apple's rebuttal, the company notes an inconvenient truth that I pointed out in my original report: For all the complaining, Microsoft actually doesn't use the term App Store to describe any of its many online stores, many of which date back several years.

Microsoft says it will continue the fight.

"We remain confident in our case and believe that the term 'App Store' should continue to be available for use by all without fear of reprisal by Apple," a Microsoft spokesperson said. "We will continue to move forward with the trademark opposition proceeding in the Trademark Trial and Appeal Board."