Umbilicus \Um`bi*li"cus\, n. [L. See Umbilic.]

1. (Anat.) The depression, or mark, in the median line of the abdomen, which indicates the point where the umbilical cord separated from the fetus; the navel.

2. (Gr. & Rom. Antiq.) An ornamented or painted ball or boss fastened at each end of the stick on which manuscripts were rolled. --Dr. W. Smith.

3. (Bot.) The hilum.

4. (Zo["o]l.)
   (a) A depression or opening in the center of the base of many spiral shells.
   (b) Either one of the two apertures in the calamus of a feather.

5. (Geom.)
   (a) One of foci of an ellipse, or other curve. [Obs.]


   (b) A point of a surface at which the curvatures of the normal sections are all equal to each other. A sphere may be osculatory to the surface in every direction at an umbilicus. Called also umbilic.

Source: Webster's Revised Unabridged Dictionary (1913)