n. - 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.
n. - A name given to some parts that resemble in shape certain bulbous roots; as, the bulb of the aorta.
n. - 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.
v. i. - To take the shape of a bulb; to swell.