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

To easily peel garlic: Microwave the entire bulb for about 20 seconds. —USA TODAY, 22 Apr. 2024

Items that will not be accepted are yard waste, tires, car batteries, used motor oil, antifreeze, herbicides, pesticides, paint, liquids of any kind, fluorescent bulbs and construction materials. —Nwa Democrat-Gazette, arkansasonline.com, 9 Apr. 2024

Plant bulbs of garlic in fall in the South, and provide them with full sun and regular water to encourage them to thrive in your garden. —Steve Bender, Southern Living, 6 Apr. 2024

The two bulbs are an A21 indoor bulb ($39.98) and a Par38 indoor / outdoor option ($34.98) and will be available only through The Home Depot, starting today. —Wes Davis, The Verge, 3 Apr. 2024

This set comes with 15 LED bulbs, which are sure to infuse your space with a soft, welcoming glow. —Christianna Silva, Better Homes & Gardens, 19 Mar. 2024

The weather-resistant lights have round bulbs that emit a warm white light. —Isabel Garcia, Peoplemag, 15 Mar. 2024

This mix of 100 bulbs is quality picked and packed directly from Holland with showy brilliant colors. —Nora Colomer, Fox News, 8 Mar. 2024

Viewers should be able to see the filament of the lightbulb, not the glow surrounding the bulb. —Eric Lagatta, USA TODAY, 31 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)
• bulb baster
• bulb-like
• compact fluorescent bulb
• compact fluorescent light bulb
• dim bulb
• incandescent light bulb
• light bulb
• olfactory 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