What does "bulb" mean?

Bulb: (Anat.) A name given to some parts that resemble in shape certain bulbous roots; as, the bulb of the aorta. Bulb of the eye, the eyeball. -- Bulb of a hair, the "root," or part whence the hair originates. -- Bulb of the spinal cord, the medulla oblongata, often called simply bulb. -- Bulb of a tooth, the vascular and nervous papilla contained in the cavity of the tooth.

Additional senses

  1. 2.An expansion or protuberance on a stem or tube, as the bulb of a thermometer, which may be of any form, as spherical, cylindrical, curved, etc. Tomlinson.
  2. 3.To take the shape of a bulb; to swell.

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