noun \ˈbəlb\

: a rounded part of some plants that is under the ground and that grows into a new plant during the growing season

: a part that has a rounded shape

Full Definition of BULB

a :  a resting stage of a plant (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 (as a tuber or corm) resembling a bulb in appearance
c :  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 \ˈbəlbd\ adjective

Examples of BULB

  1. the bulb of the thermometer

Illustration of BULB

Origin of BULB

Middle English, from Latin bulbus, from Greek bolbos bulbous plant
First Known Use: 15th century


noun \ˈbəlb\   (Medical Dictionary)

Medical Definition of BULB

: 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 : 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


noun    (Concise Encyclopedia)

In botany, the resting stage of certain seed plants, particularly perennial monocotyledons (see cotyledon), consisting of a relatively large, usually globe-shaped, underground bud with membranous or fleshy overlapping leaves arising from a short stem. The fleshy leaves function as food reserves that enable a plant to lie dormant when water is unavailable (during winter or drought) and to resume active growth when favourable conditions again prevail. There are two main types of bulbs. One, typified by the onion, has a thin papery covering protecting its fleshy leaves. The other, the scaly bulb, as seen in true lilies, has naked storage leaves, with no papery covering, making the bulb appear to consist of angular scales. Bulbs enable many common ornamentals, such as the narcissus, tulip, and hyacinth, to flower rapidly in early spring when growing conditions are favourable. Other bulb-producing plants bloom in the summer (e.g., lilies) or fall (e.g., the autumn crocus). The solid corms of the crocus and gladiolus and the elongated rhizomes of some irises are not bulbs.


Next Word in the Dictionary: bulbaceous
Previous Word in the Dictionary: Bul
All Words Near: bulb

Seen & Heard

What made you want to look up bulb? Please tell us where you read or heard it (including the quote, if possible).