Synonymous with the word Jonas. However, this is an insult directed usually at people who go out of their way to act stupid or moronic. It can also be directed at ugly clothing, like anything produced by Hannah Montana.
Girl 1: That's so fucking custy that I want to throw up my lungs.
Girl 2: That is so Miley.
Girl: You're so Miley.
Miley Cyrus: Thank you!
Girl: Only you would take that as a compliment, you fucktard.