lightbulb

n. A glass bulb with metallic contacts on the outside connected to a wire filament (usually tungsten) inside that emits light when heated by passage of electricity through the filament; -- used as the replaceable light-emitting component of an electric lamp, flashlight, lighting fixture, etc.
Syn. -- light bulb, bulb, incandescent lamp, electric light, electric-light bulb. [ WordNet 1.5 +PJC ]