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light bulb

1 ENTRIES FOUND:
light bulb noun
plural light bulbs
light bulb
noun
plural light bulbs
Britannica Dictionary definition of LIGHT BULB
[count]
: a glass bulb or tube that produces light when it is supplied with electricity
called also bulb

a light bulb goes off/on

chiefly US, informal
◊ When a light bulb goes off/on (in your head), you suddenly understand something or have a great idea.