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three-way switch[′thrē ¦wā ′swich]
An electric switch with three terminals used to control a circuit from two different points.
A switch used in house wiring when a fixture is to be turned on or off from two different locations in the house. A three-way switch must be used at each location.
An electric switch, used in conjunction with a similar switch, to control lights from two different points, as from two different ends of a hallway.