Umbilicus

1. (n.) 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. (n.) An ornamented or painted ball or boss fastened at each end of the stick on which manuscripts were rolled.
3. (n.) The hilum.
4. (n.) A depression or opening in the center of the base of many spiral shells.
5. (n.) Either one of the two apertures in the calamus of a feather.
6. (n.) One of foci of an ellipse, or other curve.
7. (n.) 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.