A person who posts on social media sites exclusively (or nearly so) in a manner intended not to further discussion, inform, or in any other meaningful way contribute to the site, but instead to cause strife, insult other users, prevent reasoned discussion, and in general make the site worse. Most seem to gain particular satisfaction from driving other users away.

Trolls are often particularly egregious on political forums, since that subject tends to bring out the worst in people.