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definitions

light bulb

noun
  1. an electric light.

Origin of light bulb

First recorded in 1880–85
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for light bulb

light bulb

noun
  1. a glass bulb containing a gas, such as argon or nitrogen, at low pressure and enclosing a thin metal filament that emits light when an electric current is passed through itSometimes shortened to: bulb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for light bulb
n.

also lightbulb, 1884, from light (n.) + bulb.

Online Etymology Dictionary, © 2010 Douglas Harper