Source : Webster's Revised Unabridged Dictionary (1913)

Cathode \Cath"ode\, n. [Gr. ? descent; ? down + ? way.]
   (Physics)
   The part of a voltaic battery by which the electric current
   leaves substances through which it passes, or the surface at
   which the electric current passes out of the electrolyte; the
   negative pole; -- opposed to anode. --Faraday.

   {Cathode ray} (Phys.), a kind of ray generated at the cathode
      in a vacuum tube, by the electrical discharge

Source : WordNet®

cathode ray
     n : a beam of electrons emitted by the cathode of an electrical
         discharge tube