The Web Analytics Associations has released an expanded set of 26 standard definitions for measuring web traffic and usage (PDF). This is a useful document for providing consensus definitions of common terms used in the web industry.
However, I find it rather ironic that they released this document only as a PDF. Come on folks! You should know better, being an association of web professionals.
(Via Shawn Zehnder Lea.)
Update: What would I recommend in addition to a PDF? A sub-site on the WAA site for the definitions, providing an index and a separate web page for each definition. Having a page for each definition would allow people to link to them directly as references. This would improve the usability of the content and enhance search engine results for those definitions (ahem).