What is "bulb of the eye"

Bulb \Bulb\ (b[u^]lb), n. [L. bulbus, Gr. bolbo`s: cf. F. bulbe.]

1. (Bot.) A spheroidal body growing from a plant either above or below the ground (usually below), which is strictly a bud, consisting of a cluster of partially developed leaves, and producing, as it grows, a stem above, and roots below, as in the onion, tulip, etc. It differs from a corm in not being solid.

2. (Anat.) A name given to some parts that resemble in shape certain bulbous roots; as, the bulb of the aort

   1. 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 bul

   2. Bulb of a tooth, the vascular and nervous papilla contained in the cavity of the tooth.

3. 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.

   3. a light bulb.