From Longman Dictionary of Contemporary Englishlight bulbˈlight bulb noun [countable] 
DTthe glass object inside a lamp that produces light and has to be replaced regularly SYN bulb
DTthe glass object inside a lamp that produces light and has to be replaced regularly SYN bulbExamples from the Corpus
light bulb• It was just that everything seemed too close, like staring at a light bulb.• Q: How many high-tech artists does it take to change a light bulb?• An outside cistern could be kept from freezing by hanging a light bulb near it and leaving it on all the time.• A small light bulb next to the assistant indicates that it has some helpful advice to offer.• I mean, look what Mr Edison, quite alone, managed to do with the light bulb! 