Definition of flue

i. S. Wales. A furnace, such as a large coal fire at or near the bottom of an upcast shaft for producing a current of air for ventilating the mine.

Ref: Fay

ii. A tube or passageway in a steam boiler for hot gases or water (depending on whether the boiler is a fire-tube or water-tube boiler).

iii. A passage or channel through which the products of combustion of a boiler or other furnace are taken to the chimney.

Ref: CTD

iv. Lanc. Shale.

Ref: Arkell