A flamethrower was a weapon that emitted fire.
An emergency services officer attempted to burn the trees that had sprung up around Green Park tube station with a flamethrower, but was unsuccessful, as the trees witheld oxygen from the fire. (TV: In the Forest of the Night)
Wooden Cybermen were equipped with flamethrowers. (TV: The Time of the Doctor)
Flamethrowers were among the attachments that could be equipped onto a Dalek's manipulator arm. Referred to by Daleks as pyro-flames, these were small cylindrical pieces at the end of the arm which shot a stream of fire to clear swaths of forest. (TV: The Daleks' Master Plan) The Daleks later used other flamethrowers, which they referred to as flame guns, to melt through ice when searching for "the Abomination". The ends resembled the Progenitor Daleks' eyestalks. (COMIC: The Only Good Dalek) Daleks in the First World War used flamethrowers to clear forests to pursue the Eleventh Doctor and his companions. The flames came from their arms. (COMIC: The Dalek Project)