Alternating current n. (Elec.) A current which periodically changes or reverses its direction of flow, especially an electric current that reverses direction sinusoidally, as is used for most domestic and industrial power requirements. Contrasted with direct curent.
Synonyms:AC Note: The common household current is alternating. Alternating current is easier than direct current to transform to high voltage and back, making long-distance transmission more efficient.
... the currents as they are generated, and supply what is called an alternating current, that is to say, a current which alternates or changes its direction several hundred times a second, or it may sift the currents as they are produced and supply what is termed a continuous current, that is, a current always in the same direction, like that of a voltaic ... — The Story Of Electricity • John Munro