(1) powerLoss in an electrical or Telecommunications system. In cables, expressed in dB per unit length, usually dB per 1000 feet, or per kilometer. This term is also used to express loss in Fiber optic cable. (2) The reduction in the Intensity of radiation, with distance from its Source due to atmospheric Absorption and/or scattering; it does not include the inverse-square decrease of intensity of Radiation with distance from the source. In a general sense, attenuation can be taken to mean any reduction of a physical variable; see also transmittance.