The Definition of Normal

My friend once asked me a simple question. "What does normal mean? If everyone is different, does that mean, different is... normal?" I didn't know how to answer. I didn't. I only said,"I guess so," smiled and changed the subject. But now that I think about it, what she said, seems true. What is the deffinition of 'Normal'? I'm not quite sure. I looked the def. in the dictionary and it says,"conforming to the standard or the common type; usual; not abnormal; regular" I just chose that deffinition out of about 10. But, everyone is different, everyone has a distinct face, feature different from another. Even twins are different! How is it possible to have the deffinition be the antonym of that exact word? Apparently it is possible. I put a lot of thought into the answer, too much maybe. The deffinition should be, in my opionion, "What people think the definition it is, because each answer is different." You may disagree with me, but again, what would the normal answer be?