dBm: Abbreviation. dB referenced to one milliwatt.

Note 1: dBm is used in communication work as a measure of absolute power values. Zero dBm equals one milliwatt.

Note 2: In DOD practice, unweighted measurement is normally understood, applicable to a certain bandwidth, which must be stated or implied.

Note 3: In European practice, psophometric weighting may be implied, as indicated by context; equivalent to dBm0p, which is preferred.

See also: Zero dBm transmission level point

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