A troll is:
A member of an internet community who continually harangues and harasses others. Someone with nothing worthwhile to add to a certain conversation, but rather continually threadjacks or changes the subject, as well as thinks every member of the forum is talking about them and only them. Trolls often go by multiple names to circumvent getting banned.
(Thanks to KnightofRa for such a “succinct” definition.)
So they are the bane of everyone’s existence, and if a troll is bothering you, report them to a mod, find a mod by checking this person’s friendlist:
Revolutioneyes: Razz must remain a paradoxal enigmatic mystery.