When ones phsycological state and disconnections with other humans makes it acceptable to invoke a response from someone via the internet, typically with an emphasis on (one of the following)

a. trying to assert ones dominance over the other
b. attempting at ones very best to gain attention

This person is typically the individual in which has little, or no friends and doesn't know much about compassion. You can also get the rare troller, whom doesn't fit any of these categories, and does it just for fun. The way to distinguish them is to pay attention to their trolling habits and how they communicate with other people. If you notice an extreme emphasis on either a or b(above) than you've got yourself someone with little or no knowledge on how to have a correct encounter with another human being.

You can never really find a troll in real-life, or if you do it'll be in the drive through or he'll be getting picked up by a relative(as he doesn't drive.) Most trolls prefer to reside in their place of trolling, typically a basement with a internet connection.(Any isolated environment from other humans.)

Being a prick on the internet because you can. Typically unleashing one or more cynical or sarcastic remarks on an innocent by-stander, because it's the internet and, hey, you can.

The art of deliberately, cleverly, and secretly pissing people off, usually via the internet, using dialogue. Trolling does not mean just making rude remarks: Shouting swear words at someone doesn't count as trolling; it's just flaming, and isn't funny. Spam isn't trolling either; it pisses people off, but it's lame.

The most essential part of trolling is convincing your victim that either a) truly believe in what you are saying, no matter how outrageous, or b) give your victim malicious instructions, under the guise of help.
Trolling requires decieving; any trolling that doesn't involve decieving someone isn't trolling at all; it's just stupid. As such, your victim must not know that you are trolling; if he does, you are an unsuccesful troll.

Signs that your trolling is succesful:
*Your victim screaming in all-caps at you.
*Personal attacks (Calling you a retard, idiot, etc).
*Being an Internet Tough Guy.
*Making a crude remark, before quickly logging off before you can retort.

Signs that your trolling is unsuccesful:
*Your victim identifying you as a troll.
*Identifying yourself as a troll.
*Your efforts being ignored.
*Being counter-trolled (See below)

Counter-trolling (Or reverse trolling) is an effective method of redeeming yourself after being trolled. It i...

Trolling is trying to get a rise out of someone. Forcing them to respond to you, either through wise-crackery, posting incorrect information, asking blatantly stupid questions, or other foolishness. However, trolling statements are never true or are ever meant to be construed as such. Nearly all trolled statements are meant to be funny to some people, so it does have some social/entertainment value.

"Trolling" isn't simply "harmful statements". Intentionally insulting/libelous statements are "flaming".

Just as bad as trolling is "Feeding the Trolls". This is when people say stuff that they know will prompt someone to respond with a trolled reply and/or replying to comments that are blatantly from a troll. This is especially true when a troll first makes his comment/reply, and (usually many) people respond, either trying to correct the troll, or express anger at the statement. At that point, the trolling was successful and has been fed. When encouraged by success and feeding, trolls often return.

Trolling is the act of purposefully antagonizing other people on the internet, generally on message boards. When done in a moderated internet community, this can result in banning. When done to uptight people such as fundies, this can result in hilarity.

Hunting for trolls.

Trollers hang around under bridges with troll guns at night (since trolls turn to stone in daylight), in the hope of bagging a troll head as a trophy.

As a VERY endangered (i.e. nonexistent) species, trolls are protected by law, and trolling is therefore illegal.

Responding through short, unhelpful, and often antagonistic means, or performing acts with the intent of getting a rise from people so it can be posted on youtube later. No longer bound to the confines of the internet.

deliberately arguing with complete fallacies on forums, comment threads, or message boards to get leets and other users pissed off by the troll's "ignorance"