Commonly used scale to rate women based on their three most important components, tits, face, and ass. A scale of 1-5 is used to judge each part of woman. A 15 would be a really hot girl with great tits and firm ass. A 0 would be, you know.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi