One who will talk shit and make another person feel bad or attempt to. They're main goal is to get a reaction out of the person they are trolling. Trolling could also be a form of payback, or retaliation to being trolled. Trolls get a thrill out of other peoples reaction and wont stop until a negative reaction is given to them. The best way to stop a troll from succeeding is to ignore them, or act passive.
Real-Life Troll : You're a virgin and you're 33 years old...You need a fucking life. Go get some sun, btw, you're whiter than a ghost.
Friend or Foe : Fuck you asshole, dick, bitch, shut the fuck up.
Real-Life Troll : *Smiles with success*