I believe that the meaning of Cool to the authors is not the slang term that is normally recognized. They believe that it is a term for individualism and a meaning of rebelliousness against anything that is possible in the world. For instance, people believe that peace, love, and charitable is cool but on the other end, other people think violence, crimes, and drugs are cool.
The term "Cool" defined in the chapter also describes that it affects the major group of young teens. Not only in their social life but the political and business aspects of it. The term cool brings out what should be consumed, what should be watched, and what should be recognized. Advertising is a key in this cool factor because it is a tool to help influence what should be cool out there.