bulb

noun

ˈbəlb 

plural bulbs

1

a

: 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

bulbed

ˈbəlbd 

adjective

flasks with bulbed necks

bulblike

ˈbəlb-ˌlīk 

adjective

or bulb-like

… a large underground rhizome, a bulblike growth that extends massive roots from its underside.

—Elizabeth Schneider

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

Viewers should be able to see the filament of the lightbulb, not the glow surrounding the bulb. —Eric Lagatta, USA TODAY, 31 Mar. 2024

In order to split this light into the whole spectrum of colors that creates white light, manufacturers paint a material called phosphor onto the diodes inside the bulb. —Natalie Wallington, Kansas City Star, 22 Mar. 2024

In early spring or fall, dig up the area around the plant and remove the new bulbs, replanting the parent bulb. —Derek Carwood, Better Homes & Gardens, 18 Mar. 2024

Garlic Garlic can be grown from grocery store bulbs by breaking apart the individual cloves within the bulb and planting them with the pointed side up and the wider root side down. —Alex Groves, Los Angeles Times, 14 Mar. 2024

Elena Petkova-Schulze began planting free bulbs from the Daffodil Project in tree beds on West 119th Street in Harlem in 2018, only to discover that someone else on her block was doing the same thing. —Jane Margolies, New York Times, 13 Mar. 2024

My personal favorite is a 40-watt-equivalent soft white bulb. —TIME, 27 Mar. 2024

Some specimens will have already formed the beginnings of a bulb at the root end. —David Tanis, San Diego Union-Tribune, 27 Mar. 2024

The flower's growth from a dormant bulb in the ground to a budding flower symbolizes the rebirth and hope of Christ’s resurrection. —Marina Johnson, The Indianapolis Star, 25 Mar. 2024

Word History

Etymology

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

First Known Use

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

Phrases Containing bulb

• a light bulb goes off/on (in someone's head)
• dim bulb
• incandescent light bulb
• light bulb
• olfactory bulb
• bulb-like
• compact fluorescent light bulb
• bulb baster
• compact fluorescent bulb

Kids Definition

bulb

noun

ˈbəlb 

1

a

: 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

b

: a fleshy structure (as a tuber or corm) resembling a bulb in appearance or function

2

: a rounded object or part shaped more or less like a bulb

a flashlight bulb

Medical Definition

bulb

noun

ˈbəlb 

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