Everything is culturally contextual. That doesn't really address what I'm saying, though.
What I am saying is that, contrary to what Christian asserted, it's possible for a definition of aikido to be non-universal without using setting, mode of dress, or social customs as criteria. A definition of aikido based on lineage, physical principles, and technique is still functional and still non-universal.
I am just pointing out that setting, mode of dress, social customs, lineage, and technique are all entirely of the same class of thing that Christian was talking about. I.e. its Fujis to Galas here. These are all things that are apt to be local to a dojo and handed from teacher to student. Their existence will be, for the most part, not due to a critical process but are more of "that's just how we do it." They are cultural.
Physical principals are possibly not on that list because you haven't defined them - and depending on how you define them, they are also going to be cultural, or they are not going to help you establish a non-universal definition of Aikido.