light bulb
noun
plural
light bulbs
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.