Perverted form of class inheritance, and one of the reasons why C++ sucks. The problem with multiple inheritance is that if you inherit the same function from two classes, there's not logical way to say which actual function should be called when the child class doesn't override the method. Also, copious use of multiple inheritance creates spaghetti inheritance structures that are a nightmare to deal with. Now which of the twenty superclasses does that function come from??

Of coure, a disciplined programmer will not let that happen, but he'll eventually have to deal with code written by undisciplined programmers who did.