• noun a channel or tube through which things such as fluids or cables can pass
  • noun a narrow passageway in a gland or bladder through which fluid leaves
  • A pipe, tube, or channel through which a substance or waves are conveyed or propagated. When referring to a pipe or tube with precise dimensions, through which microwave energy is transmitted, also called waveguide (2).
  • A pipe, tube, or channel through which lines, cables, or wires are run.
  • Within the troposphere, a layer which, depending on the temperature and humidity conditions, may act as a waveguide for the transmission of radio waves for extended distances. Also called atmospheric duct, tropospheric duct, or wave duct (2).
  • A narrow layer that forms under unusual conditions in the atmosphere or ocean, and which serves to propagate radio waves or sound waves. Also called wave duct (3).

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