Used to describe something that is full of swag and is hella fly at the same time. Often used by huge dorks to describe something or someone lame in a cool way. Most often than not, it's not usually used in a serious way, but can be depending on its intention.
A: Ha! Look what I can do with this pencil. I'm hella swy
B: Did you just say hella swy?
A: yup
B: You're hella lame, you dork.