The term Monkey Kick refers to an awkward, ineffectual kick that is just barely impactful enough to cause hogu that are rigged for electronic scoring to register a point, especially in WTF-style sparring. The Monkey Kick is often cited as an example of how the practice electronic scoring harms sport taekwondo.
Electronic hogu have embedded sensors that detect the vibration from a blow. In principle, the idea is that a legitimate taekwondo kick (such as a roundhouse kick) will impact the hogu and cause the sensors to vibrate -- thus scoring a point. Because there is no guarantee that the legitimate kick will impact directly on the sensor, the sensors need to be calibrated to detect even "light" impacts. The Monkey Kick takes advantage of this light calibration by allowing the competitor to score a point with a simple, awkward tap of the foot on the hogu, as long as the impact occurs near a sensor. In the case of a Monkey Kick specifically, this light impact is accomplished by tapping the bottom of the foot against the opponent's sensor while standing very close to the opponent.