ground glass

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Glass that has been ground or etched to create a roughened nontransparent surface.
• noun Glass that has been ground into fine particles, as for use as an abrasive.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Glass having a rough, flat surface produced by abrasion or etching

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun particulate glass made by grinding and used as an abrasive
• noun glass that diffuses light due to a rough surface produced by abrasion or etching