Definition
A villain in a story, especially in a Western (a film or other work of the Western genre).
Origins
From the black stetsons (cowboy hats) traditionally worn by such villains.
See Also
How People Actually Use It
1- A Hacker (Or rather cracker, but that's a different discussion) who uses his abilities for malicious purposes. 2- Anything relating to malicious use of the internet.
"1- as a hacker, I would have to say he's definately a black hat hacker. 2- since the software's ony use was generating registration keys for legitamite software, it was considered balck hat software."
Source: Urban Dictionary