It doesn't really stand for anything. The real term "Obi" means the wrap you use to keep a kimono together. Since it serves a similar purpose when on a CD, they also called it "obi." I've actually never seen an obi on an American CD.

The obi's are O.K. It's really the cover that counts to me, and the cover isn't even amazing. :/ I would have preferred an extention of the cover(like RAINBOW cover), or even like the obi for the "Duty" cover.