bulb

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A short, modified, underground stem surrounded by usually fleshy modified leaves that contain stored food for the shoot within.
• noun A similar underground stem or root, such as a corm, rhizome, or tuber.
• noun A plant that grows from a bulb.
• noun A rounded projection or part.
• noun A light bulb.
• noun Anatomy A rounded dilation or expansion of a canal, vessel, or organ.

from The Century Dictionary.

• noun A form of the leaf-bud, usually subterranean, in which the stem is reduced to a flat disk, rooting from the under side, and bearing above closely appressed fleshy leaves.
• noun Any protuberance or expansion resembling a bulb, especially an expansion at the end of a stalk or long and slender body: as, the bulb of a thermometer; the bulb of the aorta.
• noun plural The tonsils.
• To project or be protuberant.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb To take the shape of a bulb; to swell.
• noun (Bot.) A spheroidal body growing from a plant either above or below the ground (usually below), which is strictly a bud, consisting of a cluster of partially developed leaves, and producing, as it grows, a stem above, and roots below, as in the onion, tulip, etc. It differs from a corm in not being solid.
• noun (Anat.) A name given to some parts that resemble in shape certain bulbous roots.
• noun the eyeball.
• noun the “root,” or part whence the hair originates.
• noun the medulla oblongata, often called simply bulb.
• noun the vascular and nervous papilla contained in the cavity of the tooth.
• noun An expansion or protuberance on a stem or tube, as the bulb of a thermometer, which may be of any form, as spherical, cylindrical, curved, etc.
• noun a light bulb.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any solid object rounded at one end and tapering on the other, possibly attached to a larger object at the tapered end.
• noun A light bulb.
• noun The bulb-shaped root portion of a plant such as a tulip, from which the rest of the plant may be regrown.
• noun nautical a bulbous protuberance at the forefoot of certain vessels to reduce turbulence.
• verb intransitive To take the shape of a bulb; to swell.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun lower or hindmost part of the brain; continuous with spinal cord; (`bulb' is an old term for medulla oblongata)
• noun electric lamp consisting of a transparent or translucent glass housing containing a wire filament (usually tungsten) that emits light when heated by electricity
• noun a rounded dilation or expansion in a canal or vessel or organ
• noun a rounded part of a cylindrical instrument (usually at one end)
• noun a modified bud consisting of a thickened globular underground stem serving as a reproductive structure
• noun anything with a round shape resembling a teardrop