Source : Webster's Revised Unabridged Dictionary (1913)

Electro-magnetic \E*lec`tro-mag*net"ic\, a.
   Of, Pertaining to, or produced by, magnetism which is
   developed by the passage of an electric current.

   {Electro-magnetic engine}, an engine in which the motive
      force is electro-magnetism.

   {Electro-magnetic theory of light} (Physics), a theory of
      light which makes it consist in the rapid alternation of
      transient electric currents moving transversely to the
      direction of the ray.