1. Any of a large class of materials with highly variable mechanical and optical properties that solidify from the molten state without crystallization, are typically made by silicates fusing with boric oxide, aluminum oxide, or phosphorus pentoxide, are generally hard, brittle, and transparent or translucent, and are considered to be supercooled liquids rather than true solids.
2. Something usually made of glass, especially:
   1. A drinking vessel.
   2. A mirror.
   3. A barometer.
   4. A window or windowpane.
   5. glasses A pair of lenses mounted in a light frame, used to correct faulty vision or protect the eyes.
   6. A binocular or field glass. Often used in the plural.
   7. A device, such as a monocle or spyglass, containing a lens or lenses and used as an aid to vision.
3. 1. glasses A pair of lenses mounted in a light frame, used to correct faulty vision or protect the eyes.
   2. A binocular or field glass. Often used in the plural.
   3. A device, such as a monocle or spyglass, containing a lens or lenses and used as an aid to vision.
4. The quantity contained by a drinking vessel; a glassful.
5. Objects made of glass; glassware.

1. Made or consisting of glass.
2. Fitted with panes of glass; glazed.

1. 1. To enclose or encase with glass.
   2. To put into a glass container.
   3. To provide with glass or glass parts.
   4. To see reflected, as in a mirror.
   5. To reflect.
2. To make glassy; glaze.
3. 1. To see reflected, as in a mirror.
   2. To reflect.
4. To scan (a tract of land or forest, for example) with an optical instrument.

1. To become glassy.
2. To use an optical instrument, as in looking for game.

Our Living Language  : Common sand and glass are both made primarily of silicon and oxygen, yet sand is opaque and glass is transparent. Glass owes its transparency partly to the fact that it is not a typical solid. On the molecular level, solids usually have a highly regular, three-dimensional crystalline structure; the regularities distributed throughout the solid act as mirrors that scatter incoming light. Glass, however, consists of molecules which, though relatively motionless like a typical solid, are not arranged in regular patterns and thus exhibit little scattering; light passes directly through. At a specific temperature, called the melting point, the intermolecular forces holding together the components of a typical solid can no longer maintain the regular structure, which then breaks down, and the material undergoes a phase transition from solid to liquid. The phase transition in glass, however, depends on how quickly the glass is heated (or how quickly it cools), due to its irregular solid structure.