Definition of "Bulb" :

noun: a rounded part of a cylindrical instrument (usually at one end)

"The bulb of a syringe."

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

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