- A material medium whose physical boundaries confine and direct propagating electromagnetic waves. A waveguide, for instance, may be a hollow metallic conductor, a coaxial cable, a fiber-optic cable, or an atmospheric duct. Waveguides enable propagation of electromagnetic waves with very little attenuation. Also called guide (2).
- A waveguide (1) consisting of a hollow metal tube, and which is utilized primarily for propagating microwave energy. The cross section of such a tube may have any of various shapes, the most common being rectangular, circular, and elliptical. The waves are propagated along the longitudinal axis. Also called guide (3).