Plain English Meaning
An extra radio frequency you listen to during a PRM approach so a dedicated controller can quickly tell you to break off the approach if a nearby aircraft strays toward you.
Full Definition
A second radio frequency, separate from the tower frequency, used during simultaneous close parallel Precision Runway Monitor (PRM) approaches. The pilot monitors this frequency in addition to the tower frequency so that PRM monitor controllers can issue immediate breakout instructions if an aircraft on the adjacent parallel approach deviates toward the protected zone between runways.