Navel n. : A mark or depression in the middle of the abdomen; the umbilicus. See Umbilicus.

Navel n. : The central part or point of anything; the middle.

Navel n. : An eye on the under side of a carronade for securing it to a carriage.

Example:
How do you keep a Navel piercing clean?

Taxonomy
navel, women, umbilicus, Belly button, outie, navel tattoos, midriff, Navel fetishism, free encyclopedia, innie, Navel lint, navel gazing, umbilical hernia, colloquially, scar, humans, depression, Indian costume.

Defination from the web:
navel (also known colloquially as the belly button, or clinically as the umbilicus) is a scar on the abdomen, caused when the umbilical cord ... The navel comes in the center of the circle enclosing the spread-eagle figure in Leonardo da Vinci's Vitruvian Man, his famous drawing ...