bulb

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

electric lamp consisting of a transparent or translucent glass housing containing a wire filament (usually tungsten) that emits light when heated by electricity

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

lower or hindmost part of the brain

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

anything with a round shape resembling a teardrop