Troll can have several different meanings:

• A Troll is a fictitious, mythological creature.
  • A troll in J.R.R. Tolkien's fictional universe of Middle-earth
  • A troll in Terry Pratchett's fictional universe of Discworld
  • A troll in J K Rowling's fictional universe.
  • A troll in the Dungeons and Dragons fictional universe.
• Trolling for fish, the practice of fishing by drawing a baited line or lure behind a boat. Should not be confused with trawling, done with net.
• Trolltech is a computer software company from Oslo, Norway
• Internet trolls and Slashdot trolls are people who affect a deliberately inflammatory persona in order to provoke a vehement response from other users.
• The Fremont Troll is a piece of public art in Seattle, Washington.
• The Troll Gas Platform, one of the greatest engineering projects in history. Built by Norske Shell.
• Troll was a small Norwegian car manufacturer.
• Three Dead Trolls in a Baggie, a Canadian band known for songs like "The Toronto Song" or "The War of 1812."
• Troll is a Norwegian black metal band.
• Troll was also a Swedish pop band, remembered mainly for their single 1989 hit single "Jimmy Dean".
• Troll metal is a subgenre of black metal, itself a subgenre of heavy metal music.
• Troll tuning is one of several Norwegian folklore tunings that differs from modern Major and Minor tuning.
• In the SCA a troll is the person who collects the admission fee at an event. (Also the verb for collecting admission fees).

Additionally:

• In Middle English the word troll (derived from French troller, or 'wander') is attested from 1377 and was used to mean 'to go about, stroll'; later this term was derogatively applied to those women who followed soldiers with the purpose of prostitution; these meanings are now obsolete.
• The word troll as used to refer to the mythical creature derives from Old Norse troll, 'giant, fiend, or demon'. Possibly related to Old Norse trolldomr, 'witchcraft' and Swedish trolla 'to charm, to bewitch'.

Slang usage

• Trolling can mean walking. This is more or less basic slang now (from stroll), but it used to be polari.
• Residents of Michigan's Upper Peninsula frequently refer to residents of the state's Lower Peninsula as "trolls", making joking reference to the fact that all Lower Peninsula residents live "under a bridge" (i.e., to the south of the Mackinac Bridge that connects the state's two parts).
• Troll, Caltech slang for a student who studies hard. Also used as a verb to troll which means to study.
• Troll, derogatory term in gay male slang for an unattractive, usually overweight, gay man (implied: who is looking for sex with men). Also a verb to troll meaning to cruise for sex.