A troll may refer to any of the following:
1. On message boards, a troll or e-troll is an individual who causes others grief through frustrating behavior, or by flaming other users for various reasons. Often, trolling is considered toxic because, while occasionally humorous, it's generally not good for any online community.
When dealing with these types of people, it's best to report or ignore them. A popular phrase used online is "Don't feed the trolls," which means if you don't comment back or give them pleasure from causing grief, they eventually leave due to boredom.
"Troll" can also be used as a verb, meaning "to frustrate someone else online, either intentionally or unintentionally." For example, a user who is playing a video game poorly might apologize to his teammates by saying, "sorry everyone, I'm trolling tonight." Or, if your friend is frustrated by an another user's online comments, you might say to them, "Just ignore them, they're obviously trolling."
2. With computer games, a troll is a fictional creature found in many fantasy titles and RPGs. Trolls are generally characterized as large creatures who live in caves and don't care for humans.