Umbilicus

Part of speech: noun (n.)

1. 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. An ornamented or painted ball or boss fastened at each end of the stick on which manuscripts were rolled. Dr. W. Smith.

3. The hilum.

4. A depression or opening in the center of the base of many spiral shells.

5. Either one of the two apertures in the calamus of a feather.

6. One of foci of an ellipse, or other curve. [Obs.]

7. 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.