umbilicus

Short definition from Wiktionary

Noun

1. 1
   navel
2. 2
   Umbilical cord
3. 3
   hilum
4. 4
   A depression or opening in the center of the base of many spiral shells.
5. 5
   Either of the two apertures in the calamus of a feather.
6. 6
   A tube connecting an astronaut or spacecraft to the mothership, through which supplies and samples can be transferred.
7. 7
   One of the foci of an ellipse or other curve.
8. 8
   A point of a surface at which the curvatures of the normal sections are all equal to each other.
9. 9
   An ornamented or painted ball or boss fastened at each end of the stick on which manuscripts were rolled.