bulb / bəlb/ • n. 1. a 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 resting over winter. Compare with corm, rhizome. ∎  a plant grown from an organ of this kind. ∎  a similar underground organ such as a corm or a rhizome.2. an object with a rounded or teardrop shape like a bulb, in particular: ∎  a light bulb. ∎  an expanded part of a glass tube such as that forming the reservoir of a thermometer. ∎  a hollow flexible container with an opening through which the air can be expelled by squeezing, such as that used to fill a syringe. ∎  a spheroidal dilated part at the end of an anatomical structure.

bulb An underground plant organ that enables a plant to survive from one growing season to the next. It is a modified shoot with a short flattened stem. A terminal bud develops at the centre of its upper surface, surrounded by swollen leaf bases that contain food stored from the previous growing season. Papery brown scale leaves cover the outside of the bulb. The stored food is used in the growing season when the terminal bud produces foliage leaves and flowers. The new leaves photosynthesize and some of the manufactured food passes into the leaf bases forming a new bulb (see illustration). If more than one bud develops, then additional bulbs form, resulting in vegetative propagation. Examples of bulb-forming plants are daffodil, onion, and tulip. Compare corm.

bulb In botany, a food storage organ consisting of a short stem and swollen scale leaves. Food is stored in the scales, which are either layered in a series of rings, as in the onion, or loosely attached to the stem, as in some lilies. Small buds between the scale leaves give rise to new shoots each year. New bulbs are produced in the axils of the outer scale leaves. See also asexual reproduction

bulb An underground storage organ, comprising a short, flattened stem with roots on its lower surface, and above it fleshy leaves or leaf bases, surrounded by protective scale leaves. It may provide the means for vegetative reproduction, or for the survival of the plant from one season to the next.

bulb †onion XVI; ‘root’ of onion, etc. XVII; roundish dilatation, spec. of a glass tube XVIII. — L. bulbus = Gr. bólbos onion, bulbous root.
Hence bulbous XVI; cf. F. bulbe (XVI), bulbeux.