Source : Webster's Revised Unabridged Dictionary (1913)

Quartile \Quar"tile\, n. [F. quartile aspect, fr. L. quartus the
   fourth. See {Quart}.] (Astrol.)
   Same as {Quadrate}.

Source : WordNet®

quartile
     n : (statistics) any of three points that divide an ordered
         distribution into four parts each containing one quarter
         of the scores