[diebitter]

Did we come up with a definition?

I think heroes are those willing to sacrifice something important in order to help others.

I would certainly call firemen heroes, and astronauts too. The fact that fireman risk dangerous conditions just to help others qualifies them as such. And the fact astronauts do something incredibly risky for the benefit of mankind is something to be greatly admired.

Note sure about the rest of the initial list.