bulb

American  

[buhlb] / bʌlb /

noun

• bulbs
  plural

1. Botany.

   1. a usually subterranean and often globular bud having fleshy leaves emergent at the top and a stem reduced to a flat disk, rooting from the underside, as in the onion and lily.

   2. a plant growing from such a bud.

2. any round, enlarged part, especially at the end of a cylindrical object.

   the bulb of a thermometer.

3. Electricity.

   1. the glass housing, in which a partial vacuum has been established, that contains the filament of an incandescent electric lamp.

   2. an incandescent or fluorescent electric lamp.

4. Anatomy. any of various small, bulb-shaped structures or protuberances.

   olfactory bulb; bulb of urethra.

5. medulla oblongata.

6. Building Trades. a rounded thickening at the toe of an angle iron or tee.

7. Nautical. a cylindrical or spherical prominence at the forefoot of certain vessels.

8. Photography. a shutter setting in which the shutter remains open as long as the shutter release is depressed. B

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bulb British  

/ bʌlb /

noun

1. a rounded organ of vegetative reproduction in plants such as the tulip and onion: a flattened stem bearing a central shoot surrounded by fleshy nutritive inner leaves and thin brown outer leaves Compare corm

2. a plant, such as a hyacinth or daffodil, that grows from a bulb

3. See light bulb

4. a rounded part of an instrument such as a syringe or thermometer

5. anatomy a rounded expansion of a cylindrical organ or part, such as the medulla oblongata

6. Also called: bulbous bow. a bulbous protuberance at the forefoot of a ship to reduce turbulence

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bulb Scientific  

/ bŭlb /

1. A rounded underground storage organ that contains the shoot of a new plant. A bulb consists of a short stem surrounded by fleshy scales (modified leaves) that store nourishment for the new plant. Tulips, lilies, and onions grow from bulbs.

2. Compare corm rhizome runner tuber

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Other Word Forms

Derived Forms

• bulbed
  adjective
• bulbless
  adjective

Inflected Forms

Nouns

• bulbs
  plural

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Etymology

Origin of bulb

1560–70; < Latin bulbus < Greek bolbós onion, bulbous plant

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Explanation

A bulb is the roundish, tear-shaped part of some plants. If you plant a bulb, a flower will pop up. Bulb is also short for light bulb. Don’t try planting that kind, though, because lamps don't grow on trees. Garlic, onions, and shallots are all bulbs, and many flowering plants also grow from underground bulbs, like lilies and daffodils. A different type of bulb is a light bulb, which shares the rounded shape of the plant version. The meaning of bulb in the 16th century was simply "onion," from the Greek bolbos, "plant with round swelling on underground stem."

Example Sentences

See Examples For:

bulb bulbs

I order my tacos with avocado, a side of cebollitas asadas — bulb onions grilled until tender and charred — and a large jamaica.

From Salon ● Sep. 8, 2026

Earlier this year, when Vivienne came across a video on social media explaining the symptoms of Hypermobility Spectrum Disorder, it was like a light bulb switching on.

From BBC ● Aug. 27, 2026

A moth circling a porch light evolved to navigate by the moon; the bulb is an “evolutionary novelty” with which its ancestors never had to contend.

From The Wall Street Journal ● Jul. 24, 2026

Among the answers: a small ink-stained mahogany desk, an antique light bulb, a brown leather flight suit and a baseball jersey.

From Barron's ● May 29, 2026

There was definitely writing there—but so tiny I had to climb again onto the cot and hold the paper close to the shaded bulb.

From "The Hiding Place" by Corrie ten Boom

Some people trace the stock-market mania story back to the railroad boom in the 1800s, the South Sea Bubble in the 1700s or the Dutch mania for tulip bulbs in the 1600s.

From MarketWatch ● Oct. 27, 2026

Gallium nitride, for example, is found in much of today's lighting technology, from LED bulbs to laptop displays.

From Science Daily ● Aug. 30, 2026

Long known for its light bulbs and televisions, the Dutch consumer electronics giant has since refocused production on medical equipment.

From Barron's ● Jul. 28, 2026

“When L.A. first starting installing LEDs, most vendors only made bulbs with 4,000 Kelvins or even 5,000 Kelvins,” said Richard Yee, an engineer with Pasadena’s Department of Public Works.

From Los Angeles Times ● May 8, 2026

Afterward we’d change whatever light bulbs needed changing.

From "Okay for Now" by Gary D. Schmidt

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