A person who trolls the internet looking for people, ideas, information or organizations to drag back to a forum they belong to so forum members can ridicule, cyber-bully, harass, defame or insult their target with distortions, falsehoods, or character assassination, and engage in other acts of malice.
There are a lot of crackbots on the James Randi Educational Foundation Forum who pretend to be experts on critical thinking skills when it is clear from what they post that most members do not know the first thing about critical thinking.
Julio spent two hours screaming in my ear about how stupid some physicist was when he saw an internet article about him filing a grant application for cold fusion research. Julio was just doing his usual crackbot routine. He knows nothing about physics.