Source : Webster's Revised Unabridged Dictionary (1913)

Cation \Cat"i*on\, n. [Gr. ? downward + ? going, p. pr. of ? to
   go.] (Chem.)
   An electro-positive substance, which in electro-decomposition
   is evolved at the cathode; -- opposed to {anion}. --Faraday.

Source : WordNet®

cation
     n : a positively charged ion