A duct may refer to: Duct (anatomy), various ducts in anatomy and physiology Duct (HVAC) (Heating Ventilating and Air-Conditioning), for transfer of air between spaces in a structure Duct tape, a kind of adhesive tape Ducted fan, motor for aircraft Electrical bus duct, a metal enclosure for busbars Telecommunication Atmospheric duct, a horizontal layer in the lower atmosphere in which the vertical refractive index gradients are such that radio signals (a) are guided or ducted, (b) tend t… (More on Duct)