(Really Simple Syndication) A format for notifying new content at a website; the initials originally stood for Rich Site Summary. RSS defines rules for listing information about new content added to a website, such as the title, link and a short description (or in some cases the full body of the content), which the site publishes as an XML file at a specific URL -- in effect, a web service. This file, often called a newsfeed, can then be read and combined with feeds from other sites by news aggregators, which display the consolidated information either on a user's desktop or on a website. RSS is widely used both by news sites and by weblogs. There are four versions in widespread use: 0.91, developed by Netscape; 0.92, a modification popularized by Userland Software; 1.0, a variation based on RDF (Resource Description Framework); and 2.0, formalized in September 2002 by Userland's Dave Winer.