bulb

　　1.a modified bud consisting of a thickened globular underground stem serving as a reproductive structure

　　2.electric lamp consisting of a glass bulb containing a wire filament (usually tungsten) that emits light when heated

　　3.a rounded part of a cylindrical instrument (usually at one end);

　　the bulb of a syringe

　　4.lower or hindmost part of the brain; continuous with spinal cord; (`bulb' is an old term for medulla oblongata);

　　the medulla oblongata is the most vital part of the brain because it contains centers controlling breathing and heart functioning

　　5.a rounded dilation or expansion in a canal or vessel or organ