Real Dictionary

troll
countable noun: In Scandinavian mythology, trolls are creatures who look like ugly people. They live in caves or on mountains and steal children.
verb: If you troll somewhere, you go there in a casual and unhurried way.

troll in American English 1
to roll; revolve
to speak fast
intransitive verb: to sing with a full, rolling voice; give forth full, rolling tones
noun: a song whose parts are sung in succession; a round
transitive verb: to sing or utter in a full, rolling voice

troll in American English 2
any of a race of supernatural beings, variously conceived of as giants or dwarfs, living underground or in caves
noun: any of a race of supernatural beings, sometimes conceived as giants and sometimes as dwarfs, inhabiting caves or subterranean dwellings

troll in British English 1
noun: the act or an instance of trolling
verb: to draw (a baited line, etc) through the water, often from a boat

troll in British English 2
noun: (in Scandinavian folklore) one of a class of supernatural creatures that dwell in caves or mountains and are depicted either as dwarfs or as giants