I can give you a vague definition of cyberpunk with terms like “noir future” and “distopia,” but Rudy Rucker says it better and really whets my appetite to know more. Here’s an excerpt from What Is Cyberpunk:
Proximately, “cyberpunk” is a word coined by Gardner Dozois to describe the fiction of William Gibson. Gibson’s novel Neuromancer won the Science Fiction equivalent of the Triple Crown in 1985: the Hugo, the Nebula, and the Phil Dick award. Obviously, a lot of SF writers would like to be doing whatever Gibson is doing right. At the 1985 National SF Convention in Austin there was a panel called “Cyberpunk.” From left to right, the panelists were me, John Shirley, Bruce Sterling, a nameless “moderator,” Lew Shiner, Pat Cadigan, and Greg Bear. Gibson couldn’t make it; he was camping in Canada, and the audience was a bit disappointed to have to settle for pretenders to his crown. Sterling, author of the excellent Schismatrix, got a good laugh by announcing, “Gibson couldn’t make it today, he’s in Switzerland getting his blood changed.” Talking about cyberpunk without Gibson there made us all a little uncomfortable, and I thought of a passage in Gravity’s Rainbow, the quintessential cyberpunk masterpiece:
On Slothrop’s table is an old newspaper that appears to be in Spanish. It is open to a peculiar political cartoon of a line of middle-aged men wearing dresses and wigs, inside the police station where a cop is holding a loaf of white . . . no it’s a baby, with a label on its diaper sez LA REVOLUCION . . . oh, they’re all claiming the infant revolution as their own, all these politicians bickering like a bunch of putative mothers . . .
On the objective level, a cyberpunk work will often talk about computers, software, chips, information, etc. And on the higher level which I was talking about above, a cyberpunk work will try to reach a high level of information-theoretic complexity. High complexity does not, I should point out, mean hard to read.