Hmmmmmm...

that was a very informative post, and to be honest, according to my understanding, this meaning of Kafiroon is closer to what you have explained, than what they have said so far about it.
But honestly, I have to take yours as an opinion as well, I will put that in the list of meanings for this word, until the day comes where I can connect all the points and get the whole meaning.
So far, I have never thought of it this way, so this is totally new to me, but I will be honest, I have FELT that it might mean this way, i.e the way you explained it.
However I have known about this verse (7:172) of the testification, and with knowing that verse, and knowing "Kafir" comes from the root word "Kufr", which means "to hide, to conceal"...
So I have felt like when the messengers come to those people and to us, we all have this "Inner gut" feeling that (THIS IS IT!).. but we will hide -kufr- it because of something else.
Lets take a reference (for the sake of example not evidence) from the Biography of Muhammad, you know very well that his Uncle abu Lahab never believed in him, and the Qur'an has talked about him. There was a scene where Muhammad was asking his uncle "Why don't you believe in me when I have shown you that I'm a prophet from God"
his uncle replied "If I was convinced that you were, then I would have believed in you, but I know you are a liar so I don't think you are a messenger"
After that Muhammad leaves, and Abu Lahab tells the guy next to him "I know he is not a liar, I know he is a messenger, the reason why I refuse to believe in him is because God didn't choose a man from our sect of the Quraysh tribe to be a prophet, be he chose it from the other sect."
So as an example, I think you know now How I have understood Kufr so far...
And to me Kufr is not far away from meaning "Reject" as well... but I doubt it to be that simple...
Peace,
Thank you very much for that explanation,
Please criticize comment on my understanding,
So I may learn more, and correct my self in case I was wrong.
Yami.