Polymorphism

Question

Few days ago a person asked me a question that "How can achieve polymorphism without using overloading and overriding?".
I answered him that "it can be achieved by interface "  but he again asked me interface is not part of oops programming  it is a part of c# language  so  How will you achieve it in other language Like:
C++;
I  don't know without overloading and overriding how it is possible.

So anyone can give me a answer if there is another method of Polymorphism.

thanks.........