The ability/choice to have an awesome time regardless of (and most of the time, in spite of) non-familiarity in location, circumstance or friend count.
Named after Stewkley, a small village outside Leighton Buzzard (see: middle of nowhere) where parties are held...for some fuckin' reason.
Coined by Lee & Joe of Sketch Comedy program "The ABTV Show".
"Yeah it was just Me and Corfield, at a Morris Dancing Festival, in Skegness, on a rainy November afternoon AAAAAND we weren't suited up BUT through the power of The Stewkley Mentality it was like we were partying with Bill Murray, in Vegas, on Crystal Meth AAAAAND my penis was made out of money. The ladies loved it."