It is an expression of emotion.
The fact that humans confuse both is what is worrisome.
Think of 'The Mule' in the Foundation novels. He can convince anyone of anything because he can express any emotion without the burden of having to actually feel it.
I still remember when I cried when I was a child. It was overwhelming, and I could not stop it, but every single time there was a reason for it. And I'm sure it was, for all empirical purposes, for all that I have lived, an emotion.
Once I cried because I did miss Goldfinger on TV. You see, there's an explanation. The difference is, it was impossible to even think about stopping it. I was overwhelming.
Then one day, I was 8 or 9 years old, I cried for the last time that way. And it was not something I wanted to do, either. It just happened, I guess, as a normal part of growing up.
Let me repeat, for emphasis: I strongly disagree with your definition.
Emotions are not unexplained rational thoughts, emotions are feelings. They reside in a different part of the brain. You seem to think a hunch is an emotion.
That's just how you are programmed to be.