1. Authorization, given by an Administration, for a radio station to use a radio frequency or radio frequency channel under specified conditions
2. The process of authorizing a specific frequency, group of frequencies, or frequency band to be used at a certain location under specified conditions, such as bandwidth, power, azimuth, duty cycle, or modulation. Synonym radio frequency channel assignment. See administration (def. #1).
Source: from Federal Standard 1037C and from MIL-STD-188
See also: FCC, open spectrum