The word "umbilicus" refers to the belly button, which is the small hole or scar on the abdomen where the umbilical cord was once attached during fetal development. Full definition
All in all, it's a fairly normal activity for a biologist except that the sample I'm examining is a cross-section of my own umbilicus. (sciencemag.org)
On the contrary, Mohr (14) found significant reductions in girth at the waist and umbilicus after 4 weeks of training without appreciable loss in weight (14). (journals.lww.com)
All humans have belly buttons, but did you know that we're a very rare species that has a visible umbilicus? (smartdogowners.com)