No. A speaker can only speak with words as he understands them. It is impossible to know what other people are thinking.
A good speaker will define the words as he speaks (still relying on some baseline shared understanding of the most common words, of course; there is only so much time in the day...) so there is no room for confusion, but in absence of that it is expected that the listener will question any words that show an apparent disconnect in meaning, allowing the speaker to clear up what was meant, to ensure both parties can land on the same page.
In theory, but in practice the audience understanding is important, and communication doesn't always end up with both sides on the same page.
Even more so when it's an author/reader relationship. The reader is free to interpret the book/article/etc. how they want, and if enough agree, it becomes the consensus.
> but in practice the audience understanding is important
Where audience understanding is important than you will definitely go out of your way to ensure that definitions are made abundantly clear and that the audience agrees that they understand.
But, in actual practice, most of the time the audience understanding really doesn't matter. Most people speak for the sake of themselves and themselves alone. If the audience doesn't get it, that's their problem. Like here, it means nothing to me if you can't understand what I'm writing.
That is always the case. It may turn out that others opt to also become the audience after something is written, but that can only be determined in hindsight. Even when someone says "Oh yeah, I'll totally read what you have to write if you write it for me. Promise!", there is no guarantee they will actually follow through. More often than not they don't.
While the work is being written, the author is the only known audience. In practice, if an author cannot find enough motivation to write something for himself, it simply won't get written. Anyone else who happens to become the audience is gravy, but the work cannot be written for them as they only become known as an audience later.
Probably from listening to another speaker who defined it, adopting their definition. Possibly from making it up on the spot. After all, someone has to create the first definition! Words weren't handed down to us by some magical deity.
But that doesn't mean the audience came from the same place. It is very possible, and often happens, that they heard/created an entirely different definition for the same word. The speaker cannot possibly use their definition before even knowing of it.
A good speaker will define the words as he speaks (still relying on some baseline shared understanding of the most common words, of course; there is only so much time in the day...) so there is no room for confusion, but in absence of that it is expected that the listener will question any words that show an apparent disconnect in meaning, allowing the speaker to clear up what was meant, to ensure both parties can land on the same page.