navel -
a scar where the umbilical cord was attached; "you were not supposed to show your navel on television"; "they argued whether or not Adam had a navel"; "she had a tattoo just above her bellybutton"
navel -
The central part or point of anything; the middle.
Wikipedia
The navel (clinically known as the umbilicus, also known as the belly button) is a scar on the abdomen, caused when the umbilical cord is removed from a newborn baby. All placental mammals have a navel. It is fairly conspicuous in humans.
OmegaWiki Dictionary
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navel A scar where the umbilical cord was attached.