Google (GOOG) wants to brand its eyeglass wearable technology with the single word “Glass,” rather than “Google Glass,” but the U.S. Patent and Trademark Office has rejected the search giant’s bid for the nameplate.

Last fall, Google applied for a trademark for the word “Glass,” using the same font as it does now in its marketing materials for its already trademarked “Google Glass,” according to an account in The Wall Street Journal. Google doesn’t need a trademark to use the word “Glass” in marketing and branding materials but the patent agency’s rubber stamp would make it easier for the vendor to protect the name against infringement by competitors.

But so far Google’s bid for the name has been rejected, owing in part to its similarity to current or pending trademarks for software also containing the word “glass.” Consumers might be confused by overlap in the use of the word “glass,” the patent agency said.

The agency’s second objection, however, is a bit more definitive and may be difficult for Google to overcome. Because the word “glass” merely describes Google’s product but doesn’t reflect on the distinct nature of the product, it can’t be trademarked. That’s no different than if a company making donuts wanted to trademark the phrase “powdered sugar.”

As expected, Google’s trademark attorneys answered the patent office’s denial with a long defense of the application, arguing that no consumer confusion would result from its use of the word “glass,” particularly considering the amount of exposure Google’s eyewear technology already has received prior to mass production of the device. And, the vendor took exception to the agency’s “descriptive” argument, contending the frame and display for Google Glass is made of titanium and plastic with no glass material used.

The Journal noted that Border Stylo, a Los Angeles-based developer that makes a browser extension called “Write on Glass” has objected to Google’s trademark application, to which Google’s lawyers have responded with a petition to cancel the company’s trademark.