Search一下不难吧？
http://en.wikipedia.org/wiki/Troll_(Internet)In Internet slang, a troll is someone who posts inflammatory, extraneous, or off-topic messages in an online community, such as a forum, chat room, or blog, with the primary intent of provoking readers into an emotional response or of otherwise disrupting normal on-topic discussion. The noun troll may also refer to the provocative message itself, as in: "That was an excellent troll you posted."