Definition of pentile:
(n) :
(statistics) Any of the four points that divide an ordered distribution into five parts, each containing a fifth (20%) of the population. Used commonly for income distributions.
(n) :
(statistics) Any one of the five groups.
(n) :
Obsolete form of pantile (“type of roof tile”). [A type of interlocking roof tile with a rounded under and over, giving it an elongated S-shaped (ogee) cross section.]