Definition of bulb in English:

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Pronunciation: /bəlb/


1A rounded underground storage organ present in some plants, notably those of the lily family, consisting of a short stem surrounded by fleshy scale leaves or leaf bases and lying dormant over winter. Compare with corm, rhizome.
Example sentences
  • Snowdrops hate having their roots disturbed, but dividing them in spring allows their roots to recover and gives the leaves time to feed the bulb before they become dormant later in summer.
  • No matter what your climate, be sure to water planted bulbs throughout the winter.
  • It is a good time to buy and plant conifers and evergreens, summer-flowering bulbs and dahlia tubers.
1.1A plant grown from a bulb.
Example sentences
  • I also have two small bulbs which are one piece rather than divided into cloves - they grew from bulbils and if replanted will grow into proper divided bulbs next year.
  • Garlic grows in bulbs with even cloves enclosed in a white or pink skin.
  • It is also difficult to identify garlics by appearance, since cloves from the same bulb grow differently in different locations.
2An object with a rounded or teardrop shape like a bulb, in particular.
Example sentences
  • A pneumatic bulb is required to accurately assess the tympanic membrane and the aeration of the middle ear.
  • The rubber bulb that inflates the cuff may be hard to squeeze.
  • The surgeon gently pumps in air with the bulb attachment.
2.1A light bulb.
Example sentences
  • The reason for this is, if replacement bulbs have a different voltage or wattage to the original set, your lights will be dimmer or brighter and this will overload the light chain and permanently damage the set.
  • Events through the week include a light bulb amnesty at which normal light bulbs can be exchanged for low-energy bulbs donated by Yorkshire Electricity.
  • Also, that you know the wattage of the bulb and your electric rates.
2.2An expanded part of a glass tube such as that forming the reservoir of a thermometer.
Example sentences
  • It was a narrow glass tube with a bulb at the bottom.
  • Crookes's tube consisted of a glass bulb, from which most of the air had been removed, encasing two metal plates called electrodes.
  • Yesterday, all the bulbs in my galileo thermometer were up the top.
2.3A hollow flexible container with an opening through which the air can be expelled by squeezing, such as that used to fill a syringe.
Example sentences
  • Nicola took out a small medicine bottle with a bulb syringe, and began with delicate squeezes of the bulb to collect the moisture that gathered at the corners of the child's eyes.
  • Gently put the compressed bulb into the open nostril.
  • Release pressure (let the air back in) on the bulb until the nose is clear.
2.4A spheroidal dilated part at the end of an anatomical structure.
Example sentences
  • For the sense of smell, odors are processed in an area of the brain called the olfactory bulb.
  • If it is exactly in the midline, it may be the duodenal bulb, the pylorus, or the distal antrum.
  • An anomalous carotid artery or jugular bulb may present in a similar fashion.


Late Middle English: via Latin from Greek bolbos 'onion, bulbous root'.

For editors and proofreaders

Syllabification: bulb

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