Would you like to have a go at answering that question? Interpret it as you wish. I am interested in people's thoughts, to help me in preparing a couple of seminars. It is quite difficult to come up with a definition that covers all aspects of heroism.
My thought for a snappy definition would be something along the lines of: "A hero is somebody who does what is right regardless of the consequences." There is also the aspect of being a role model that isn't covered there.