Navel

n. small dimple in the abdomen where the umbilical cord was once attached to the placenta; belly button (Informal); center

Distinguish from naval (i.e., relating to a navy). The navel, also called a belly button, or umbilicus, is a scar on the abdomen, caused when the umbilical cord is removed from a newborn baby. All placental mammals have a navel. While it is fairly conspicuous in humans, in most mammals it appears only as a thin hairless line.
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Navel /na·vel/ the umbilicus. na·vel n. The mark on the surface of the abdomen that indicates where the umbilical cord was attached to the fetus [more]Navel - Community and Resources

Noun
1. scar where the umbilical cord was attached
(synonym) umbilicus, bellybutton, omphalos, omphalus
(hypernym) point
(part-holonym) abdomen, venter, stomach, belly
2. the center point or middle of something
(synonym) navel point
(hypernym) center, centre, midpoint

n. navel, umbilicus, omphalos, belly button