The Collaborative International Dictionary of English v.0.48:

Alternating current \Al"ter*nat`ing cur"rent\ (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.

   Syn: AC
        [Webster 1913 Suppl. +PJC]

   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.
         [PJC]

The Collaborative International Dictionary of English v.0.48:

electric current \electric current\, electrical current
\electrical current\,
   the movement of electrically charged particles, atoms, or
   ions, through solids, liquids, gases, or free space; the term
   is usually used of relatively smooth movements of electric
   charge through conductors, whether constant or variable.
   Sudden movements of charge are usually referred to by other
   terms, such as spark or lightning or discharge. In
   metallic conductors the electric current is usually due to
   movement of electrons through the metal. The current is
   measured as the rate of movement of charge per unit time, and
   is counted in units of amperes. As a formal definition, the
   direction of movement of electric current is considered as
   the same as the direction of movement of positive charge, or
   in a direction opposite to the movement of negative charge.
   Electric current may move constantly in a single direction,
   called direct current (abbreviated DC), or may move
   alternately in one direction and then the opposite direction,
   called alternating current (abbreviated AC).
   [PJC]

WordNet (r) 3.0 (2006):

alternating current
    n 1: an electric current that reverses direction sinusoidally;
         "In the US most household current is AC at 60 cycles per
         second" [syn: alternating current, AC, alternating
         electric current] [ant: DC, direct current, direct
         electric current]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "alternating current":
   AC, DC, absorption current, active current, conduction current,
   convection current, cycle, delta current,
   dielectric displacement current, direct current,
   displacement current, eddy current, electric current,
   electric stream, emission current, exciting current,
   free alternating current, galvanic current, high-frequency current,
   idle current, induced current, induction current,
   ionization current, juice, low-frequency current,
   magnetizing current, multiphase current, pulsating direct current,
   reactive current, rotary current, single-phase alternating current,
   stray current, thermionic current, thermoelectric current,
   three-phase alternating current, voltaic current, watt current