The Collaborative International Dictionary of English v.0.48:

Nombril \Nom"bril\, n. [F. nombril, for OF. lombril, i. e.,
   ombril, with the article, a dim. fr. L. umbilicus the navel.
   See Navel.] (Her.)
   A point halfway between the fess point and the middle base
   point of an escutcheon; -- called also navel point. See
   Escutcheon.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Navel \Na"vel\ (n[=a]"v'l), n. [AS. nafela, fr. nafu nave; akin
   to D. navel, G. nabel, OHG. nabolo, Icel. nafli, Dan. navle,
   Sw. nafle, L. umbilicus, Gr. 'omfalo`s, Skr. n[=a]bh[imac]la.
   [root]260. See Nave hub, and cf. Omphalic, Nombril,
   Umbilical.]
   1. (Anat.) A mark or depression in the middle of the abdomen;
      the umbilicus; called also belly button in humans. See
      Umbilicus.
      [1913 Webster]

   2. The central part or point of anything; the middle.
      [1913 Webster]

            Within the navel of this hideous wood,
            Immured in cypress shades, a sorcerer dwells.
                                                  --Milton.
      [1913 Webster]

   3. (Gun.) An eye on the under side of a carronade for
      securing it to a carriage.
      [1913 Webster]

   Navel gall, a bruise on the top of the chine of the back of
      a horse, behind the saddle. --Johnson.

   Navel point. (Her.) Same as Nombril.
      [1913 Webster]

WordNet (r) 3.0 (2006):

navel point
    n 1: the center point or middle of something; "the Incas
         believed that Cuzco was the navel of the universe" [syn:
         navel, navel point]