Microsoft has once again filed opposition to Apple's efforts to trademark the phrase "App Store."

In a new reply filed with the U.S. Patent and Trademark Office to get Apple's trademark application refused, Microsoft rebutted Apple's rebuttal from earlier this month. This is the same one Microsoft knocked for breaking the rules by being too long and using a smaller font size to get in more of an argument.

"The undisputed facts establish that 'app store' means exactly what it says, a store offering apps, and is generic for the retail store services for which Apple seeks registration," the company wrote in today's filing. "Apple does not contest that its other services are ancillary and incidental to its retail store services. Summary judgment should be entered denying Apple's application in its entirety."

In the nine-page document (PDF), Microsoft takes aim at Apple's defense of the trademark, which made use of testimony from Robert A. Leonard to show that "App Store" was in fact a proper noun and had proven itself to be tied to Apple ahead of competitors.

Microsoft struck back in a separate declaration filed today by linguistic expert Ronald R. Butters that attempts to poke holes in Leonard's claims, saying "the compound noun 'app store' means simply 'store at which apps are offered for sale,' which is merely a definition of the thing itself--a generic characterization."

Butters also knocks Leonard's sourcing of online dictionaries that had spelled out Apple's ties to the App Store moniker. "The online 'dictionary' sources Leonard cites were not written by established lexicographers and are without scientific authority," Butters wrote. "Even so, he included an online source that does, in fact, define app store as a generic term."

Microsoft's legal battle against Apple over the use of the App Store name began in January, with Microsoft filing arguments that the phrase was too generic. Since then the companies have traded blows for and against the 2008 patent filing, with Microsoft attempting to preserve its general use, in part, to keep it from becoming a permanent part of Apple's trademark portfolio.

Besides Apple's legal tussle with Microsoft over the controversial trademark filing, the company has gone on the offense against Amazon for calling its new mobile software distribution marketplace the "Appstore," filing a lawsuit just last week.