This is one of the things that drives me *CRAZY* about Aikido. Here you see *one* art that's only 60-80 years old (heck, we can't even agree on that!) and we can't even have a discussion about it using terms that we all understand. Yet in the past when I've tried to elicit a discussion about what it actually is, everyone poo-poos it like some absurd question because anyone who actually studies the art would know it immediately.
Honestly, in the JSA communities, you just don't see this. I've had conversations with people from dozens of different ryu-ha ranging from 20-400 years in age and we all manage to understand what the other is talking about. Sure you get lots of, "Ah, I see what you're doing, we don't do that." or "Aha, we call that X not Y." But here in Aikido, this amazing unifying art, we can't even agree on what the @#$% word Aikido means.
There's no agreement on terms and definitions because if one were to define what the terms mean, it would automatically point out that some portion of the community wasn't actually doing what some other portion of the community is. As long as everything remains amorphous and ill defined we can all claim that these differences are simply stylistic, alternative methods.
The plain fact is, much if not most Aikido out there is not being done with any amount of what the other "aiki" arts would agree to call "aiki". Most Aikido practitioners can't define what "aiki" means from the standpoint of waza. They're great on the Cosmic balance stuff but most can't tell you what makes a technique "aiki" and what doesn't. I often ask people to tell me what they think "aiki" is when I teach seminars and almost no one can actually clearly describe what is going on.
You can see this in the discussions about the definition of "aiki" on the language thread. Most Aikido folks have some idea that "aiki" is about avoiding the energy of an attack but their idea of waza is some sort of physical manipulation which is really what I would call a sort of jiu jutsu and not really "aiki" at all.
For this reason I don't see the community arriving at better and more precise definitions. It would make the inconsistencies too apparent...