[1] : The Collaborative International Dictionary of English v.0.48

quartile \quar"tile\, n. f. quartile aspect, fr. l. quartus the
   fourth. see quart. astrol.
   same as quadrate.
   1913 webster
see also:
quart quadrate 

[2] : WordNet (r) 2.0

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

Quartile >> Q Words
Quartile, definition of term: Quartile
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