ground glass

Optics. glass that has had its polished surface removed by fine grinding and that is used to diffuse light.

glass that has been ground into fine particles, especially for use as an abrasive.

Origin of ground glass

First recorded in 1840–50

In this case the pictures were not projected upon the screen, but were upon a ground-glass plate which the observer looks at.

Magic, Stage Illusions and Scientific Diversions Including Trick Photography |Albert A. Hopkins
Leighton had seen little of Balcomb for a year or more, and his friend's name on the ground-glass door arrested his eye.

The Wit and Humor of America, Volume VII. (of X.) |Various
The solid grey walls simply glowed and dulled like a ground-glass bulb when its light is switched on and off.

Down the Yellowstone |Lewis R. Freeman
"Boy to see you, sir," he said briefly, as he closed the ground-glass door behind him.

Lucy Maud Montgomery Short Stories, 1896 to 1901 |Lucy Maud Montgomery

It was lighted by large, ground-glass, French globe-lamps, suspended from the ceiling at equal distances.

The Memoirs of Harriette Wilson, Volumes One and Two |Harriette Wilson

ground glass

glass that has a rough surface produced by grinding, used for diffusing light

glass in the form of fine particles produced by grinding, used as an abrasive