A hair color, common in most areas of the word. The second most common hair color, next to black. It is characterized by higher levels of dark pigment eumelanin and lower levels of the pale pigment phaeomelanin.
Most of the other defintions for "brunette" is full of bullshit. Brown hair isn't any more attractive than blonde hair or redhair, and to judge someone by physical appearance is shallow and idiotic. There are beautiful, elegant blondes (Scarlett Johansson, Charlize Theron), and beautiful, elegant brunettes (Angelina Jolie, Catherine Zeta-Jones). And of course there are redheads, which can be equally as stunning.
Oh, and by the way, most of the stupid bimbo blondes you see have either bleached their hair, assuming that guys think it's "cute", or have succumbed to peer pressure and decided, "Well, I guess I'll just act stupid because everyone already thinks that I am."
Idiot: Oh, she's a brunette, she must be really smart, but boring.
Intelligent Person: You dumbass. Hair color has nothing to do with personality or intelligence, you piece of shit.