umbo

  1. Noun.  (biology) A boss, or rounded elevation, or a corresponding depression, in a palate, disk, or membrane; as, the umbo in the integument of the larvæ of echinoderms or in the tympanic membrane of the ear.
  2. Noun.  (zoology) One of the lateral prominence just above the hinge of a bivalve shell.
  3. Noun.  (mycology) A bump or protrusion on the top of the cap.
  4. Noun.  (historical) The boss of a shield, at or near the middle, and usually projecting, sometimes in a sharp spike.

This is an unmodified, but possibly outdated, definition from Wiktionary and used here under the Creative Commons license. Wiktionary is a great resource. If you like it too, please donate to Wikimedia.

This entry was last updated on RefTopia from its source on 3/20/2012.