The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

   Cathode ray (Phys.), a kind of ray generated at the cathode
      in a vacuum tube, by the electrical discharge.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cathode ray
    n 1: a beam of electrons emitted by the cathode of an electrical
         discharge tube