plural bulbs
: 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
: a fleshy structure (such as a tuber or corm) resembling a bulb in appearance
: a plant having or developing from a bulb
: 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
: a rounded or swollen anatomical structure
: a camera setting that indicates that the shutter can be opened by pressing on the release and closed by ending the pressure
bulbed adjective
flasks with bulbed necks
bulblike adjective
or bulb-like
… a large underground rhizome, a bulblike growth that extends massive roots from its underside. Elizabeth Schneider

Illustration of bulb

Illustration of bulb
  • 1 hyacinth
  • 2 onion
  • 3 tulip
  • 4 lily

Examples of bulb in a Sentence

the bulb of the thermometer
Recent Examples on the Web Daylight bulbs are best for task lighting in places such as kitchens, offices and ceiling fixtures. Cameron Sullivan, The Mercury News, 8 Feb. 2024 Theo couldn’t understand how Shirlee could be so calm and cool in there: the room smelled strongly of piss, and the watery light from the bulb made Theo’s eyes ache. Addie Citchens, The New Yorker, 5 Feb. 2024 Flip on a porch light on a summer evening and, within minutes, bugs will begin to congregate near the bulb. Sarah Kuta, Smithsonian Magazine, 31 Jan. 2024 In addition, the yacht is equipped with twin rudders and a telescopic lifting keel with a 27-ton bulb that can reduce the draught from 20 feet to 13. Rachel Cormack, Robb Report, 8 Jan. 2024 The lantern-style light has an attractive bronze exterior with wavy glass walls, and the special LED bulb inside has a warm orange hue that flickers to mimic a candle flame. Camryn Rabideau, Peoplemag, 19 Jan. 2024 Each bulb produces 2-3 stems and blooms for 7-9 weeks indoors through the colder months. Miranda Crowell, Better Homes & Gardens, 18 Jan. 2024 Walmart already puts items such as video games, nicotine gum and replacement bulbs for car headlights behind lock and key. Craig Silverman, ProPublica, 17 Jan. 2024 Every light source had to be natural — noon sun was noon sun, natural moonlight was natural moonlight — or had to come from the oil lamps, electric bulbs or candles in the Höss house. Scott Roxborough, The Hollywood Reporter, 8 Jan. 2024 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'bulb.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


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

First Known Use

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

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

Dictionary Entries Near bulb

Cite this Entry

“Bulb.” Dictionary, Merriam-Webster, Accessed 23 Feb. 2024.

Kids Definition


: an underground resting stage of a plant (as an onion or tulip) consisting of a short stem base bearing one or more buds enclosed in overlapping leaves
: a fleshy structure (as a tuber or corm) resembling a bulb in appearance or function
: a rounded object or part shaped more or less like a bulb
a flashlight bulb

Medical Definition


: 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
: a rounded part: as
: a rounded enlargement of one end of a part see bulb of the penis, bulb of the vestibule, end bulb, hair bulb, olfactory bulb
: medulla oblongata
broadly : the hindbrain exclusive of the cerebellum
: a thick-walled muscular enlargement of the pharynx of certain nematode worms

More from Merriam-Webster on bulb

Last Updated: - Updated example sentences
Love words? Need even more definitions?

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