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

Etymology

Origin of bulb

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

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

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

On the drive home, Scanlon, 33, had a light bulb moment: “What I love doing is something most people find totally overwhelming and exhausting,” she says.

From Los Angeles Times ● May 21, 2026

A bright bulb above the door never went out.

From "Fallout: Spies, Superbombs, and the Ultimate Cold War Showdown" by Steve Sheinkin

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

Absorbed students carefully threaded wires into junction boxes to make circuits connected to lights, bulbs flickering on one by one to signal a job well done.

From Barron's ● Jul. 8, 2026

Instead, performance slumped and he retired in February 2000, scribbling a message on his office whiteboard: “Tulip bulbs for sale”—a reminder of 17th-century speculation in the Dutch flower market.

From The Wall Street Journal ● Jun. 1, 2026

They reach their greatest densities in the UK's woods where many thousands of bulbs can exist in one woodland, creating the incredible blue carpets associated with spring.

From BBC ● May 10, 2026

With her telling him exactly how she wanted it, he had wired for dozens of bulbs to be screwed into the floor at what she called stage front, and other bulbs dangled from the ceiling.

From "Cold Sassy Tree" by Olive Ann Burns

Related Words

• corn