Well, it can be a noun, but most wikis and other sites cite it as an offensive term:


That being said, I think transgender people should give some leeway. How the hell is the average person supposed to conclude that the term is offensive? There are a lot of people that shorthand "Jap" for "Japanese person," unaware of how offensive that actually is. Apparently, even the way Mangsi advised us to use it ("a transgender person") is deemed offensive by Wiktionary.