bulb

noun

1.
a modified bud consisting of a thickened globular underground stem serving as a reproductive structure
Derived from:
bulbaceous
2.
electric lamp consisting of a transparent or translucent glass housing containing a wire filament (usually tungsten) that emits light when heated by electricity
3.
a rounded part of a cylindrical instrument (usually at one end)
Derived from:
bulbous
4.
anything with a round shape resembling a teardrop
Derived from:
bulblike
5.
lower or hindmost part of the brain; continuous with spinal cord; (‘bulb’ is an old term for medulla oblongata)
Derived from:
bulbar
6.
a rounded dilation or expansion in a canal or vessel or organ
Derived from:
bulbous