What is the definition of cool?

I saw a Paul Weller tribute band last night and the topic of conversation turned to the man himself. While the women thought the Modfather needed a bit of a makeover, the men were in full agreement that he epitomised cool. The guys thought he had the swagger and loved his image - some in the pub even copied it - while the girls were adamant he was starting to look a bit jaded. So what is the definition of cool? Personally I think Johnny Depp is cool - he always looks stylish and has an air of mystery. But it is Weller who has influenced the fashion worn by guys of all ages. James Dean, Marlon Brando - there have been many cool characters over the years and it looks like Weller has joined the list.