"Both"? I only gave one definition which I thought had only one way to understand it. What's the other one?
Even if there were a medium in which light exclusively had a constant speed (this is the idea behind the Lorentz Ether Theory), it's pointless to defend that concept because it is impossible to identify the state of that medium, unless you know something that none of the rest of us are privileged to know, in which case, I beg you to share it with us.
You better be careful. Crackpots tend to get themselves banned on this forum. We're here to teach and learn about relativity in this universe, not speculating about some other universe. I think it can safely be said that you may have a lot to learn, but if not, you cannot teach something that is contrary to the accepted theory of relativity. Please take this with the right attitude and if you are not familiar with the rules of this forum, please read them before proceeding. I hate to see another person get banned.