Cosmic noise: Random noise that originates outside the Earth's atmosphere.

Note: Cosmic noise characteristics are similar to those of thermal noise. Cosmic noise is experienced at frequencies above about 15 MHz when highly directional antennas are pointed toward the Sun or to certain other regions of the sky such as the center of the Milky Way Galaxy. Synonym galactic radio noise.

Source: from Federal Standard 1037C and from MIL-STD-188

See also Radio astronomy for a sources of, and information derived from cosmic noise.