water glass

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

• noun A drinking glass or goblet.
• noun An open tube or box having a glass bottom for making observations below the surface of the water.
• noun A water gauge made of glass.

from The Century Dictionary.

• noun A glass water-gage to indicate to the eye the level of the water in a steam-boiler.
• noun A water-clock or clepsydra.
• noun An instrument for making observations be neath the surface of water, consisting of a tube with a glass bottom; a water-telescope.
• noun Same as soluble glass (which see, under glass).

from the GNU version of the Collaborative International Dictionary of English.

• (Chem.) See Soluble glass, under glass.
• A clepsydra.
• An instrument consisting of an open box or tube with a glass bottom, used for examining objects in the water, as upon the sea bottom in shallow places.
• A water gauge for a steam boiler.

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

• noun inorganic chemistry A common name for some water-soluble silicate compounds, especially when occurring in dissolved, jelly-like form.

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

• noun clock that measures time by the escape of water
• noun a viscous glass consisting of sodium silicate in solution; used as a cement or as a protective coating and to preserve eggs
• noun a glass for drinking water
• noun gauge for indicating the level of water in e.g. a tank or boiler or reservoir