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

decil \dec"il\, decile \dec"ile\, n. f. d'ecil, fr. l. decem
   ten? cf. it. decile. astrol.
   an aspect or position of two planets, when they are distant
   from each other a tenth part of the zodiac, or 36deg.
   1913 webster deciliter

[2] : WordNet (r) 2.0

decile
     n : statistics any of nine points that divided a distribution
         of ranked scores into equal intervals where each interval
         contains one-tenth of the scores

Decile >> D Words
Decile, definition of term: Decile
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