What is the meaning of Oculus?

A window or other opening that has an oval or circular shape (as of an eye).

1. The central boss of a volute.
2. An opening at the apex of a dome.

   The central boss of a volute.

   An opening at the apex of a dome.

   oculus

   eye

   :

   1. sight, vision
   2. luminary of the sun and stars
   3. spot resembling an eye, such as on a peacock feather
   4. :
      1. eye, bud, bourgeon
      2. bud, bulb or knob on many roots, on the reed, etc.
      3. great houseleek

         sight, vision

         luminary of the sun and stars

         spot resembling an eye, such as on a peacock feather

         :

         1. eye, bud, bourgeon
         2. bud, bulb or knob on many roots, on the reed, etc.
         3. great houseleek

            eye, bud, bourgeon

            bud, bulb or knob on many roots, on the reed, etc.

            great houseleek

            :

            1. principal ornament
            2. eye of the soul, mind's eye

            principal ornament

            eye of the soul, mind's eye

            Source: wiktionary.org