noun light down, such as rises from cotton, fur, ·etc.; very fine lint or hair.
2. flue ·noun a compartment or division of a chimney for conveying flame and smoke to the outer air.
3. flue ·add. ·noun in an organ flue pipe, the opening between the lower lip and the languet.
4. flue ·noun a passage way for conducting a current of fresh, foul, or heated air from one place to another.
5. flue ·noun an inclosed passage way for establishing and directing a current of air, gases, ·etc.; an air passage.
6. flue ·noun a pipe or passage for conveying flame and hot gases through surrounding water in a boiler;
distinguished from a tube which holds water and is surrounded by fire. small flues are called fire tubes or simply tubes.