Pronunciation: (flOO),[key] —n. 1. a passage or duct for smoke in a chimney.
2. any duct or passage for air, gas, or the like.
3. a tube, esp. a large one, in a fire-tube boiler.
4. Music. a. See flue pipe. b. Also calledwindway. a narrow slit in the upper end of an organ pipe through which the air current is directed.