- An evacuated glass bulb containing a metal filament which is heated by electrical resistance to produce light.
- (by extension) An article that resembles such a bulb and converts electricity to light by any process.
- a fluorescent light bulb
- an LED light bulb
- (figurative) Used in reference to the sudden arrival of a realization, an inspiration, an idea, or the like.
- a light bulb moment
- 1949, in Forbes (magazine), volume 64, page 18:
- Figuratively speaking, a light-bulb flashed over Galvin's head early this year, and in March–along […]
- 2010, Sandy Abrams, Your Idea, Inc., Abrams Media, →ISBN, page xi:
- A light bulb went off in my head as I had an incredible idea for a beauty product.
evacuated glass bulb containing a metal filament that produces light