The Collaborative International Dictionary of English v.0.48:

Voltage \Vol"tage\, n. (Elec.)
   Electric potential or potential difference, expressed in
   volts.
   [1913 Webster]

WordNet (r) 3.0 (2006):

voltage
    n 1: the rate at which energy is drawn from a source that
         produces a flow of electricity in a circuit; expressed in
         volts [syn: voltage, electromotive force, emf]
    2: the difference in electrical charge between two points in a
       circuit expressed in volts [syn: electric potential,
       potential, potential difference, potential drop,
       voltage]

The Free On-line Dictionary of Computing (30 December 2018):

voltage
potential difference

    (Or "potential difference", "electro-motive
   force" (EMF)) A quantity measured as a signed difference
   between two points in an electrical circuit which, when
   divided by the resistance in Ohms between those points,
   gives the current flowing between those points in Amperes,
   according to Ohm's Law.  Voltage is expressed as a signed
   number of Volts (V).  The voltage gradient in Volts per metre
   is proportional to the force on a charge.

   Voltages are often given relative to "earth" or "ground" which
   is taken to be at zero Volts.  A circuit's earth may or may
   not be electrically connected to the actual earth.

   The voltage between two points is also given by the charge
   present between those points in Coulombs divided by the
   capacitance in Farads.  The capacitance in turn depends on
   the dielectric constant of the insulators present.

   Yet another law gives the voltage across a piece of circuit as
   its inductance in Henries multiplied by the rate of change
   of current flow through it in Amperes per second.

   A simple analogy likens voltage to the pressure of water in a
   pipe.  Current is likened to the amount of water (charge)
   flowing per unit time.

   (1995-12-04)