Microsoft is challenging Apple’s trademark filing of “App Store” claiming it’s a generic term that should be available for all competitors to use.

[ad#Google Adsense 300×250 in story]However, Apple used Microsoft’s own trademark fight against it.

“Having itself faced a decades-long genericness challenge to its claimed WINDOWS mark, Microsoft should be well aware that the focus in evaluating genericness is on the mark as a whole and requires a fact-intensive assessment of the primary significance of the term to a substantial majority of the relevant public,” says Apple in the filing. “Yet, Microsoft, missing the forest for the trees, does not base its motion on a comprehensive evaluation of how the relevant public understands the term APP STORE as a whole.”

According to TechFlash, Apple also included quotes from linguistics expert, who concluded that “the predominant usage of the term APP STORE is as a proper noun to refer to Apple’s online application marketplace.”

Apple first started the App Store to sell applications for its iPhone, iPod and later iPad.