While hated by most, these people are typically non-social for reasons beyond their control, and manage to get that one glimpse at society by eliciting responses from forum-goers who, nine times out of ten, think they know everything and that anything that goes against the norm is bad. There are of course the assholes who do it just for fun, but a lot of these people are suffering: people with manic (or often just plain old) depression, people with real issues in real life, or people who's real life isn't as cupcakes and unicorns as people on the internet assume.

I say this because I know people in real life who many would consider trolls, and they "troll" on forums because they receive no attention from their family and very little from anyone else. They are saints for putting up with it in real life, but it'd be unhealthy to pent up all their frustration. So what do they do? They speak out on the internet, often in obnoxious and annoying matters. The very fact that people respond to what they say is important to them, just because they get satisfaction in knowing that some people somewhere acknowledge their existence, and perhaps more importantly their opinion. Believe me, most trolls you see aren't "a poor excuse of a human being". Their lives in real life is worse than many could imagine. Everyone needs to vent sometimes.

One who posts a deliberately provocative message to a newsgroup or message board with the intention of causing maximum disruption and argument

One who purposely and deliberately (that purpose usually being self-amusement) starts an argument in a manner which attacks others on a forum without in any way listening to the arguments proposed by his or her peers. He will spark of such an argument via the use of ad hominem attacks (i.e. 'you're nothing but a fanboy' is a popular phrase) with no substance or relevence to back them up as well as straw man arguments, which he uses to simply avoid addressing the essence of the issue.

1a. Noun
One who posts a deliberately provocative message to a newsgroup or message board with the intention of causing maximum disruption and argument.

1b. Noun
A person who, on a message forum of some type, attacks and flames other members of the forum for any of a number of reasons such as rank, previous disagreements, sex, status, ect.
A troll usually flames threads without staying on topic, unlike a "Flamer" who flames a thread because he/she disagrees with the content of the thread.

1c. Noun
A member of an internet forum 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.


2a. Noun
Sometimes compared to the Japanese ‘Oni’, a troll is a supernatural creature of Scandinavian folklore, whose race was thought to have carried massive stones into the countryside (although actually the result of glaciers). Lives in hills, mountains, caves, or under bridges. They are stupid, large, brutish, hairy, long-nosed, and bug-eyed, and may also have multiple heads or horns. Trolls love to eat ...

1. A large, brutish creature of European myth, often lacking in intelligence. Sometimes compared to the Japanese oni.
2. A dumbass who makes idiotic posts in message boards newsgroups for the sole purpose of pissing people off, often lacking in intelligence. Sometimes compared to people who pass you by on the sidewalk then grab you in inappropriate places.

One of many unsung internet heroes who are almost entirely misunderstood. Contrary to popular belief, many trolls are actually quite intelligent. Their habitual attacks on forums is usually a result of their awareness of the pretentiousness and excessive self-importance of many forum enthusiasts. As much as people may hate trolls, they are highly effective - their actions bring much of the stupidity of other forum users out into the great wide open.

Someone who is purposefully posting on a forum/messageboard/site sith the sole aim to irritate the regular members.

Contrary to popular belief there is much more to internet trolling than posting "OMG UR ALL SO GHEYYYY!!!1" "OMFG TRIVIUM SUX ASS U FAGS LOL" and the like. People who post such things will usually be one-post wonders and get banned, however the more experienced troll will attempt to cause some sort of havoc under the admins radar.

Common examples of trolling:
The long-term troll:
These guys don't mind waiting around for the fun to begin. They may pretend to be an average n00b, and give themselves the stereotyical interest(s) of the average member of said forum, then once having a few posts they will gradually try to spread dissent. This type may even pretend to be pally to the admin and get their msn (and try to crack their account password of course) whilst causing general disruption. May act under other proxies and slate these fake trolls on msn to the aforementioned gullible admin. These people, to be frank, usually have no life and love bringing message boards to their knees by putting considerable time into their carnage. If they crack the admins password the board is doomed.

The sophisticated troll:
This type will usually have some sort of distaste for whatever the said message board is discussing and try to cause annoyance as opposed to destructiveness. They will parody the members and see how much they can get over their heads. Subtle piss...

A person who posts to a forum or other form of online communication to disrupt or cause widespread argument.