Dictionary.net

(tap) A passive device used in cablesystems to divide and combine radio frequency signals. Adirectional coupler has at least three ports: line in, lineout, and the tap. The signal passes between line in and lineout ports with loss referred to as the insertion loss. Asmall portion of the signal power applied to the line in portpasses to the tap port. A signal applied to the tap port ispassed to the line in port less the tap attenuation value.The tap signals are isolated from the line out port to preventreflections. A signal applied to the line out port passes tothe line in port and is isolated from the tap port. Somedevices provide more than one tap output line (multi-taps).