A "Forum Troll" is a person who posts outrageous message to provoke people to respond.
The Forum Troll delights in sowing discord within a forum.
A troll is someone who inspires flaming rhetoric, someone who is deliberately controvertial, baiting and pulling people into a "flaming" discussion.
Flaming discussions usually end with name calling, a flame war and at best a locked thread or in extreme cases a deleted thread.
Trolling is a form of harassment that can completely monopolize a forum discussion.
Well meaning defenders can create chaos simply by responding to trolls. The more responses a troll gets the more ammunition he has to stir things up further.
The best response is to ignore a troll starve them of the food they live on, or to report a message to a forum moderator. Most moderators will usually delete troll messages or simply delete their accounts. (source)
-JGIG