Cool as you please!

I often think about this 'being cool' thing.We all want to be or at least have wanted to be 'cool' at times, to be popular and liked, to be reckoned as a cool guy/girl whatever. Even I have, and still do at times. But what is it we mean by it? It's a bit ironic that I must ask you what it means, for I added this 'cool' option in my poll only minute ago.
So, basically, who do you say is cool? Somebody good-looking, slim or athletic, in trendy or designer clothes, always ready with the right lines, funny and blah blah blah? Somebody who's always pulling pranks? The school-champion? The hot model? The rock singer?Will you call a character like Hermione Granger cool(forget Emma Watson)-just think about it, if you knew a girl like her in school or college, bushy hair, bookworm, large front-teeth-would you call her cool? What is the definition of being cool? And then there are the people whom you don't know and have never met. Recently, I was in this forum of a Harry Potter website where we had a thread called "^The Person Above You...." where each person had to say something about the user posting before him/her. And the most common adjective used was, you guessed it, 'cool'. Is cool then a quality we ascribe on people when we can't think of anything else?
I will end with a couple of qoutations from the HP books- just think about it-

"He(Harry) would have liked Cho to discover him sitting with a very cool group of people laughing their heads off at a joke he had just told; he would not have chosen to be sitting with Neville and Loony Lovegood, clutching a toad and dripping in Stinktap." (book5)
" 'People expect you to have cooler friends than us, ' said Luna, once again displaying her knack forembarrassing honesty.
'You are cool,' said Harry shortly. ' None of them was at the ministry. They didn't fight with me.' " (book6)
Let me know what you think!