used to elaborate one's mood/ opinion.
used often in negative connotation or in the course of a state of shock and bewilidered.
Often used by skateboarders and their wannabes in the California, Northern U.S. regions, and Canadians.
It was once used in the show Degrassi, as well.
I can't believe your mom let you get that hella sick video game!
Dude, your wheels on your board are hella bad; get them fixed!