Definitions by BlackHatKnight

Blackhat 

(Somebody using) optimization tricks that artificially boost search engines rankings, using methods that usually break the search engines' TOS.
Examples of blackhat techniques are cloaking, stuffing pages with keywords or links and using unnatural redirects.
The term was inspired by old western movies' villains always using a black cowboy hat.

See also SEO Spam and black hat SEO.

Blackhat by Blackhatknight July 16, 2008

BLTN 

Better Late Than Never

"I forgot to give you your birthday present yesterday. Ah well, BLTN."

BLTN by BlackHatKnight December 28, 2005

blackhat 

(Somebody using) optimization tricks that artificially boost search engines rankings, using methods that usually break the search engines' TOS.
Examples of blackhat techniques are cloaking, stuffing pages with keywords or links and using unnatural redirects.
The term was inspired by old western movies' villains always wearing a black cowboy hat.

Ref.: SEO Spam and black hat SEO.

blackhat by BlackHatKnight June 5, 2005