Wikipedia
Meaconing is the interception and rebroadcast of navigation signals. These signals are rebroadcast on the received frequency, typically, with power higher than the original signal, to confuse enemy navigation. Consequently, aircraft or ground stations are given inaccurate bearings.
Meaconing is more of a concern to personnel in navigation ratings than to radio operators. However, communications transmitters are often used to transmit navigation signals. Since communications personnel operate the transmitters, they must know how to deal with any communications problems resulting from meaconing.
Successful meaconing can cause aircraft to be lured into "hot" (ambush-ready) landing zones or enemy airspace, ships to be diverted from their intended routes, bombers to expend ordnance on false targets, or ground stations to receive inaccurate bearings or position locations.
The term 'meacon' is a portmanteau of masking beacon.