alternating current

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An electric current that reverses direction in a circuit at regular intervals.

from the GNU version of the Collaborative International Dictionary of English.

• (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun an electric current in which the direction of flow of the electrons reverses periodically having an average of zero, with positive and negative values (with a frequency of 50 Hz in Europe, 60 Hz in the US, 400 Hz for airport lighting, and some others); especially such a current produced by a rotating generator or alternator.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an electric current that reverses direction sinusoidally