In internet slang, a troll is a person who posts inflammatory, insincere, digressive, extraneous, or off-topic messages in an online community (such as social media (Twitter, Facebook, Instagram, etc.), a newsgroup, forum, chat room, or blog), with the intent of provoking readers into displaying emotional responses, or manipulating others' perception. This is typically for the troll's amusement, or to achieve a specific result such as disrupting a rival's online activities or manipulating a political process. Even so, Internet trolling can also be defined as purposefully causing confusion or harm to other users online, for no reason at all.

Both the noun and the verb forms of "troll" are associated with Internet discourse. Media attention in recent years has equated trolling with online harassment. The Courier-Mail and The Today Show have used "troll" to mean "a person who defaces Internet tribute sites with the aim of causing grief to families". In addition, depictions of trolling have been included in popular fictional works, such as the HBO television program The Newsroom, in which a main character encounters harassing persons online and tries to infiltrate their circles by posting negative sexual comments.