A: Most people use the terms interchangeably. However, technically, there is a difference. With guitar pickups, “coil splitting” refers to breaking the connection between the two coils in a humbucking pickup so that one is disabled and the remaining one functions as a single-coil pickup.
“Coil tapping,” on the other hand, refers to taking the signal from a location within a single-coil pickup’s coil of wire, rather than at the end of the coil. This is done to reduce the output of the pickup; the more turns of wire the coil has, the higher its output. By tapping the coil somewhere in the middle, the output is reduced. This feature is commonly found on higher-output single-coil pickups such as Seymour Duncan’s Quarter Pounders, which can be tapped to produce an output more similar to a vintage Fender single-coil. Coil tapping could also be used to tap off the signal from a humbucking pickup from somewhere within one of the coils, though this is much less commonly done.