1a device by which a flow of liquid or gas from a pipe or container can be controlled: she turned the cold tap on the air-supply tap (also tapping) British an electrical connection made to some point between the end terminals of a transformer coil or other component. 2a device connected to a telephone for listening secretly to someone’s conversations: those taps produced hundreds of hours of recordings an act of listening secretly to someone’s telephone conversation.
3an instrument for cutting a threaded hole in a material. 1draw liquid through the tap or spout of (a cask, barrel, or other container): several barrels had been tapped to celebrate old victories draw (liquid) from a cask, barrel, or other container: in the cellars of the monasteries the butlers were tapping new and old ale draw sap from (a tree) by cutting into it. 2exploit or draw a supply from (a resource):clients from industry seeking to tap Edinburgh’s resources of expertise [no object]:these magazines have tapped into a target market of consumers informal obtain money or information from (someone):he considered whom he could tap for information 3connect a device to (a telephone) so that conversation can be listened to secretly:the telephones were tapped by the state security police
4cut a thread in (something) to accept a screw: on most vices, the metal jaws are drilled and tapped to accept screws