An Acronym for Wireless Markup Language.
This is an XML-based MarkupLanguage specifically tailored for user agent software running on WAP devices. (As for any XML application, if you go from HTML straight to WML, chances are you'll find it very strict.) The user agents are commonly referred to as micro browsers in reference to their WebBrowser-like role but limited capabilities. The WAP devices they run on often impose even more limitations.