pia mater: Meaning and Definition of

pi•a ma•ter

Pronunciation: (pī'u mā'tur, pē'u), [key]
— Anat. Anat.
  1. the delicate, fibrous, and highly vascular membrane forming the innermost of the three coverings of the brain and spinal cord. Cf.(def. 6),
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.