groundmass: Meaning and Definition of

ground•mass

Pronunciation: (ground'mas"), [key]
— n.
  1. the crystalline, granular, or glassy base or matrix of a porphyritic or other igneous rock, in which the more prominent crystals are embedded.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.
See also: