Source : Webster's Revised Unabridged Dictionary (1913)

Organist \Or"gan*ist\, n. [Cf. F. organiste.]
   1. (Mus.) One who plays on the organ.

   2. (R. C. Ch.) One of the priests who organized or sung in
      parts. [Obs.]

Source : WordNet®

organist
     n : a person who plays an organ