: 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
… 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
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This bulb allows for scheduling and scene creation to personalize your lighting experience.—Nora Colomer
May Earn A Commission If You Buy Through Our Referral Links. This Content Was Created By A Team That Works Independently From The Fox Newsroom., FOXNews.com, 3 July 2025 Other thoughtful features include crank lift and tilt capabilities, a rust-resistant pole, fade-resistant canvas, and energy-efficient bulbs.—Mariana Best, Better Homes & Gardens, 2 July 2025 There are 15 tough plastic bulbs on 48 feet of cable.—Simon Hill, Wired News, 26 June 2025 Old-fashioned incandescent bulbs waste up to 90% of their energy, but LED bulbs convert that same amount into visible light, helping to deliver energy savings of up to 90%.—Benny Har-Even, Forbes.com, 24 June 2025 See All Example Sentences for bulb
Word History
Etymology
Middle English, from Latin bulbus, from Greek bolbos bulbous plant
: 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
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