Veganism is a way of living which seeks to exclude, as far as is possible and practicable, all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose.
That's like RCs saying they have the authoritative definition of christianity
Nope. :) There's no schism in veganism, and I believe that Donald Watson, the founder of the Vegan Society, helped create the definition. The VS really is the key organisation worldwide.
No, I'm not. I'm talking about veganism:
https://www.vegansociety.com/go-vegan/definition-veganism
(This is the authoritative definition.)