Troll

Troll is a slang for a person who posts inflammatory, insincere, digressive, extraneous, or off-topic messages in an online community, 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.