1) Light fixture 
Vitrite, also known as foam glass, is a very low fusing point black glass mainly used for the insulation base of electric lamps. It was formerly made by the Vitrite Company. ==Process== To make the electric lamp, molten vitrite is poured into the shell up to a height of approximately a quarter inch (6 millimeters). A plunger is brought down to for...
• (n.) A kind of glass which is very hard and difficult to fuse, used as an insulator in electrical lamps and other apparatus.
Vit'rite noun [ Latin vitrum glass.] A kind of glass which is very hard and difficult to fuse, used as an insulator in electrical lamps and other apparatus. 
vitrite 1. A kind of glass which is very hard and difficult to fuse. 2. A reference to an insulator in electrical lamps and other apparatus (apparatuses).