from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An electric light in which a filament is heated to incandescence by an electric current.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. An evacuated glass bulb containing a metal filament which is heated by electrical resistance to produce light.
- n. An article that resembles such a bulb and converts electricity to light by any process.
- n. Used in reference to the sudden arrival of a realization, an inspiration, an idea, or the like.
light + bulb, from Middle French bulbe, from Latin bulbus ("bulb, onion"), from Ancient Greek βολβός (bolbos, "plant with round swelling on underground stem"). (Wiktionary)