1. (n.) A spherical 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.

2. (n.) A name given to some parts that resemble in shape certain bulbous roots; as, the bulb of the aorta.

3. (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.

4. (v. i.) To take the shape of a bulb; to swell.

ball balloon bilge bladder blain bleb blister blob boll bolus boss bow bubble bulbil bulblet bulge bulla bump bunch burl button cahot chine clump condyle convex corm dowel ear ellipsoid flange flap gall geoid globe globelet globoid globule glomerulus gnarl gob gobbet handle hill hump hunch jog joggle knob knot knur knurl lip loop lump mole mountain nevus nub nubbin nubble oblate spheroid orb orbit orblet papilloma peg pellet prolate spheroid radicle radix rhizome rib ridge ring rondure root rootstock shoulder sphere spheroid spherule spine stud style tab tap taproot tuber tubercle tubercule verruca vesicle wale wart welt