DEFINITION
FLUE:
• (n.) An inclosed passage way for establishing and directing a
current of air, gases, etc.; an air passage
• (n.) A compartment or division of a chimney for conveying flame
and smoke to the outer air.
• (n.) A passage way for conducting a current of fresh, foul, or
heated air from one place to another.
• (n.) 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.
• (n.) Light down, such as rises from cotton, fur, etc.; very fine
lint or hair.