[1] : The Collaborative International Dictionary of English v.0.48

umbo \um"bo\, n.; pl. l. umbones, e. umbos. l.
   1. the boss of a shield, at or near the middle, and usually
      projecting, sometimes in a sharp spike.
      1913 webster

   2. a boss, or rounded elevation, or a corresponding
      depression, in a palate, disk, or membrane; as, the umbo
      in the integument of the larvae of echinoderms or in the
      tympanic membrane of the ear.
      1913 webster

   3. zool. one of the lateral prominences just above the
      hinge of a bivalve shell.
      1913 webster umbonate
see also:
umbones umbos 

[2] : WordNet (r) 2.0

umbo
     n : a slight rounded elevation where the malleus attaches to the
         eardrum
     also: umbones pl
see also:
umbones 

Umbo >> U Words
Umbo, definition of term: Umbo
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