Troll

"Troll" means someone who causes unpleasant mischief. Trolls post inflammatory questions, comments or answers, or even create questions/comments/answers pretending to be someone else such as a young user. These malicious people have their fun, get reported, get banned, then created a new account and come back. Many people are trying to get users to completely ignore trolls so they'll get bored and go away. But plenty of people still allow themselves to get angry and post angry responses -- which of course is sweet bliss to the troll. Alternatively, a "troll" means someone who's older and on the lecherous side.