Bulb

noun

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

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

   Synonymslight bulblightbulbincandescent lampelectric light

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

   “the bulb of a syringe”

4. anything with a round shape resembling a teardrop

5. 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”

   Synonymsmedulla oblongatamedulla

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