Okay.... "Is" is a form of "be". So what does it mean to be? To think? I think, therefore I am?
I think that "is" is one of those words that we always use, and we know what it means even if we can't acurrately give it a solid, concrete definition. I think the one Dictionary.com had to offer is just as clear as any other.
We could say the the state of "being" is "subjective" and therefore a different experience for everyone who "is," but that leaves us even more confused, and in desperate need of something to clear up the abstractions. The word "is" becomes obscure-
"The dog is brown."
"I perceive the dog to be brown."
Is the dog really brown? What if the dog bit a child and the police need a description of it so as to catch it? Would you say "it was a brown dog" or "It appeared to be brown?" Is it wrong to assum that because you see the dog as brown, others will too?
In the world of philosophy and convoluted language that accounts for all the "what-ifs" associated with words, this kind of dissection might be kind of interesting. I think in the real world, it's irrelevent though, at least this particular word, because it's so universal. There are just some things we assume are perceived the same way by everyone- "The dog is brown," "It's raining outside," "The ground is hard," etc. Saying "The ground feels hard to me" doesn't change the fact that pretty much everyone will agree, so what's the point? I'm sure there is one... in the world of a debate forum... but when I fall off my front porch, I'm not going to be worrying about the true meaning of "is" and the eprceptions about the ground that other people have. The ground is hard, and falling on it hurts. In my mind, that's a fact.
"I'm thinking about leaving tomorrow
I'm thinking about being on my own
I think I been wasting my time
I'm thinking about getting out"