umbilicus

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Biology A small opening or depression similar to a navel, as the hollow at the base of the shell of some gastropod mollusks, one of the openings in the shaft of a feather, or the hilum of a seed.

from The Century Dictionary.

• noun In anatomy and zoology, the more or less nearly central point in the walls of the abdomen where the yolk-bag or umbilical vesicle of the embryo hangs, or where the navel-string or umbilical cord enters the belly; the navel; the omphalos.
• noun Hence Some navel-like formation; some circumscribed depression or elevation; a sort of button, or a place in which a button might fit: when elevated instead of depressed, oftener called umbo.
• noun In botany: [capitalized] An old generic name (A. P. de Candolle, 1801) for the navelwort, Cotyledon Umbilicus.
• noun The part of a seed by which it is attached to the placenta; the hilum. See cut under hilum.
• noun A depression or an elevation about the center of a given surface.
• noun In antiquity, an ornamented or painted ball or boss fastened upon each end of the stick on which manuscripts were rolled.
• noun In geometry, a term used by the older geometers as synonymous with focus; in modern works, a point in a surface through which all lines of curvature pass.
• noun The raised central boss of a large plateau or dish, often made to fit the hollow foot of the ewer which stands upon it and forms one design with the dish.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Anat.) The depression, or mark, in the median line of the abdomen, which indicates the point where the umbilical cord separated from the fetus; the navel; the belly button, in humans.
• noun (Gr. & Rom. Antiq.) An ornamented or painted ball or boss fastened at each end of the stick on which manuscripts were rolled.
• noun (Bot.) The hilum.
• noun A depression or opening in the center of the base of many spiral shells.
• noun Either one of the two apertures in the calamus of a feather.
• noun obsolete One of the foci of an ellipse, or other curve.
• noun A point of a surface at which the curvatures of the normal sections are all equal to each other. A sphere may be osculatory to the surface in every direction at an umbilicus. Called also umbilic.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun anatomy navel

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a scar where the umbilical cord was attached