Merriam Webster Definition: a way of thinking, behaving, or doing something that has been used by the people in a particular group, family, society, etc., for a long time.
When I hear the word tradition used by Buddhist practioners, I believe they mean a practice that has been around for a long time as in the dictionary usage of the word. When I probe further, in my opinion, they are referring to a practice that was developed by their teacher or by their teacher’s teacher.
In my case, my teacher, Maezumi Roshi, was considered very untraditional when I met him. His father was a well-established Japanese Soto Zen teacher and Maezumi Roshi spent his college years practicing Zen in a Dojo run by Koryu Roshi. Koryu Roshi was the head of the Shakyamuni Kai, a lay group of Zen teachers and students whose main study was koan study. Maezumi Roshi was also studying with Yasutani Roshi who founded the San Bo Kyo Dan a group of Zen teachers (both lay and ordained) that practices koan study, shikantaza and breathing practices.
Maezumi Roshi created many new forms of practice and also taught us the forms he learnt from his teachers. He constantly told me to create new forms of study that would be relevant in this time and place (western countries.) I believe that I have done that and have been labeled as untraditional. In my opinion, I have followed a tradition that I inherited from my teacher and from my genes.
Coming from a Jewish heritage and founding the Zen Peacemakers Order of DisOrder, I love the Jewish word mishegass which Leo Rosten defines as:
I prefer to use mishegass instead of tradition when I hear folks talk about their Buddhist Tradition.
After all, Shakyamuni Buddha is quoted as expressing the opinion that the only constant in life is that life is constantly changing.