\ ˈbəlb How to pronounce bulb (audio) \
plural bulbs

Definition of bulb

1a : a resting stage of a plant (such as the lily, onion, hyacinth, or tulip) that is usually formed underground and consists of a short stem base bearing one or more buds enclosed in overlapping membranous or fleshy leaves
b : a fleshy structure (such as a tuber or corm) resembling a bulb in appearance
c : a plant having or developing from a bulb
2 : a bulb-shaped part specifically : a glass envelope enclosing the light source of an electric lamp or such an envelope together with the light source it encloses
3 : a rounded or swollen anatomical structure
4 : a camera setting that indicates that the shutter can be opened by pressing on the release and closed by ending the pressure

Illustration of bulb

Illustration of bulb

bulb 1a: 1 hyacinth, 2 onion, 3 tulip, 4 lily

Other Words from bulb

bulbed \ ˈbəlbd How to pronounce bulb (audio) \ adjective
flasks with bulbed necks
bulblike \ ˈbəlb-​ˌlīk How to pronounce bulb (audio) \ or bulb-like adjective
… a large underground rhizome, a bulblike growth that extends massive roots from its underside. — Elizabeth Schneider

Examples of bulb in a Sentence

the bulb of the thermometer
Recent Examples on the Web Unlike some other smart lights, this dimmable LIFX bulb does not require a bridge or hub. Marc Saltzman, USA TODAY, 19 June 2022 Add an old-fashioned Edison bulb—one of which is included with this model—to complete the look. Rachel Klein, Popular Mechanics, 16 June 2022 All projectors have slightly different throw lengths, based on the type of bulb, lens, and other factors used in their design. Parker Hall, Wired, 8 June 2022 Many others who had planted earlier succeeded in harvesting, going from plant to plant, slicing the poppy’s bulb, then scooping up the sap that oozes out, the raw material for opium. Abdul Khaliq, The Christian Science Monitor, 3 June 2022 With the heat wave expected to expand into more humid, coastal regions, the risk of hitting critical wet-bulb temperature thresholds will increase, Otto said. Denise Chow, NBC News, 7 May 2022 Using a bulb meal (5-10-5, for example) in the planting hole will help the bulbs establish a strong root system once they are replaced in the soil. oregonlive, 1 May 2022 The decision comes down to traditional bulb lamps, lasers, or LEDs. Mike Richard, Men's Health, 28 Apr. 2022 Today Twitter is like Hoover Dam, with all its raging power put to use lighting one 40-watt bulb. David Gelernter, WSJ, 11 May 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'bulb.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of bulb

15th century, in the meaning defined at sense 1a

History and Etymology for bulb

Middle English, from Latin bulbus, from Greek bolbos bulbous plant

Learn More About bulb

Time Traveler for bulb

Time Traveler

The first known use of bulb was in the 15th century

See more words from the same century

Dictionary Entries Near bulb




See More Nearby Entries 

Statistics for bulb

Last Updated

26 Jun 2022

Cite this Entry

“Bulb.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/bulb. Accessed 29 Jun. 2022.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

More Definitions for bulb


\ ˈbəlb How to pronounce bulb (audio) \

Kids Definition of bulb

2 : a dormant stage of a plant that is formed underground and consists of a very short stem with one or more flower buds surrounded by special thick leaves
3 : a plant structure (as a tuber) that is somewhat like a bulb
4 : a rounded object or part the bulb of a thermometer


\ ˈbəlb How to pronounce bulb (audio) \

Medical Definition of bulb

1 : a rounded dilation or expansion of something cylindrical the bulb of a thermometer especially : a rounded or pear-shaped enlargement on a small base the bulb of an eyedropper
2 : a rounded part: as
a : a rounded enlargement of one end of a part — see bulb of the penis, bulb of the vestibule, end bulb, hair bulb, olfactory bulb
b : medulla oblongata broadly : the hindbrain exclusive of the cerebellum
c : a thick-walled muscular enlargement of the pharynx of certain nematode worms

More from Merriam-Webster on bulb

Nglish: Translation of bulb for Spanish Speakers

Britannica English: Translation of bulb for Arabic Speakers

Britannica.com: Encyclopedia article about bulb


Test Your Vocabulary

Odd Habits and Quirks

  • image1926873504
  • Which of the following best describes an easily irritated person?
True or False

Test your knowledge - and maybe learn something along the way.

Universal Daily Crossword

A daily challenge for crossword fanatics.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!