What is a master?

A master, defined by T'ai Chi Master Al Huang in Part 1, Chapter 1 of The Dancing Wu Li Masters, is simply someone who started before you did.

If I started before you, I am a master to you; if you started before me, you are a master to me. The lesson to be taken from this is that we are all masters, and also all students. Each one of us has something to learn from every other one of us. We do not always know in what subject another person is a master for us; therefore, we must always keep our minds and eyes open, ready to learn from everyone. Everyone is a teacher, and everyone is a student. Are you ready to teach and to learn?