A phrase used to negate something that you just said so that you can then say what you actually think.
Larry: The book looks great, Jason. Having said that, I would consider it more of a pamphlet than a book. It's looking a little thin.
A statement of questionable legitimacy. There is usually little or no evidence to back up a stoner fact, however the maker of the statement will insist that his or her information is accurate and act as if it is common knowledge. The term derives from the suspect statements often made by stoners
Josh: "Coughing gets you like ten times higher, man."
Spiegel: "Yeah, right. That is such a stoner fact."
Josh: "No, I'm serious, man, everyone knows it's true."
Spiegel: "Sure it is. Next you're going to be telling me that if my roommate dies, I'll get straight A's."