Bridging loss is the loss, at a given frequency, that results when an impedance is connected across a transmission line. It is expressed as the ratio, in decibels, of the signal power delivered to a given point in a system downstream from the bridging point prior to bridging, to the signal power delivered to the given point after bridging.
Source: from Federal Standard 1037C and from MIL-STD-188
References
Bridging loss Wikipedia(Text) CC BY-SA