Watch the The "Shwonk" online guitar lesson by Geoff Hartwell from Guitar Lab: Electric Slide
This is a technique that got its name from a friend of mine, David Koltai, of Pigtronix effects. It’s an articulation technique that can be applied to just about any single note, but the idea is to use it sparingly to add emphasis. This is one of those techniques that you may stumble across inadvertently while playing or improvising, but can be difficult to reproduce. I realize it can be frustrating, but take it slow, stay relaxed, and I guarantee you’ll find a lot of uses for this one!