Trolling - a 'troll' is someone who posts rude, offensive, or derogatory messages on the Internet. Trolls post on sites such as blogs, online discussion forums, bulleting boards etc, with the intent of aggravating or disrupting discussion of the participants. A 'troll' can define the message itself or can be used as a verb meaning to post such messages. For example: "Someone was trolling our discussion forum today."
*Wikipedia [link]
