Any material substance, such as fiber-optic cable, twisted-wire pair, coaxial cable, dielectric-slab waveguide, water, and air, that can be used for the propagation of signals, usually in the form of modulated radio, light, or acoustic waves, from one point to another. Note: By extension, free space can also be considered a transmission medium for [..]

A means of transferring intelligence from point to point; includes light, smoke, sound, wire lines, and radio-frequency waves.

(physics) any material substance which can propagate waves or energy