Slang term for Madisonville, Kentucky - seat of Hopkins County. Typically used to artificially inflate the importance and level of activity of this backwater town. Commonly used when referring to anticipated illegal party behavior - including, but not limited to: consumption of alcohol by minors, marijuana usage, and often consensual (but underage) sexual activity.
The term "Madvegas" may also be found in use in a sarcastic manner, often by former residents of Madisonville who have moved away from the area to other parts of the country - commonly referred to as "escaping".
Joe: "Are we headed to Madvegas tonight?"
Sam: "Hell yeah man! Jake's bringing the weed and the Crown, and there's gonna be pussy on tap!"
It's true - I used to live in a little place called Madisonville, a.k.a. Shithole, U.S.A. Heh, good ol' Madvegas. Thank God I escaped that place.