Mean that something, whatever it is, is very extreme.. and girls tend to say it way too much in those high school movies..
Jessi: "Hey Amy, did you hear that mike stabbed James and turned to hulk then smashed his head and ate his insides and scratched his face?"
Amy: "Oh.. really?"
Jessi: "Yeah you should've seen his face it was SO UGLY, like, oh my god!!!!"