/ Dictionary / Index P pial: Meaning and Definition of Find definitions for: pi•al Pronunciation: (pī'ul, pē'-), [key] — adj. of or pertaining to the pia mater. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Piagetian pia mater Related Content Daily Word Quiz: maritime Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language