Acrynym for "Good Bye Cruel World!". Often found on blogs or forums when a member disagrees with a particular subject matter to such a degree that they decide to leave the forum/blog forever. In doing so, they often feel compelled to leave a last message explaining why they feel so wronged/slighted and how they will never post again -- this is the GBCW message.

Literally everyone, ever. Including the writer of this definition.