Definitions

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

  • noun The boss or knob at the center of a shield.
  • noun Biology A knoblike protuberance arising from a surface, as the prominence near the hinge of a bivalve shell or the raised area in the center of the cap of a mushroom.
  • noun Anatomy A small projection at the center of the outer surface of the eardrum.

from The Century Dictionary.

  • noun The boss of a shield, central in the case of a circular shield.
  • noun A boss or knob.

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

  • noun The boss of a shield, at or near the middle, and usually projecting, sometimes in a sharp spike.
  • noun A boss, or rounded elevation, or a corresponding depression, in a palate, disk, or membrane.
  • noun (Zoöl.) One of the lateral prominences just above the hinge of a bivalve shell.

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

  • 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.
  • noun zoology One of the lateral prominence just above the hinge of a bivalve shell.
  • noun mycology A bump or protrusion on the top of the cap.
  • noun historical The boss of a shield, at or near the middle, and usually projecting, sometimes in a sharp spike.

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

  • noun a slight rounded elevation where the malleus attaches to the eardrum

Etymologies

from The American Heritage® Dictionary of the English Language, 4th Edition

[Latin umbō, umbōn-; see nobh- in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

Borrowed from Latin umbo

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Examples

  • Running upward and slightly forward from the umbo is a reddish-yellow streak produced by the manubrium of the malleus.

    XII. Surface Anatomy and Surface Markings. 2. Surface Markings of Special Regions of the Head and Neck 1918

  • For example, these bivalve shells, probably arks (Arcidae), each had a hole thru its umbo.

    Archive 2009-04-01 AYDIN 2009

  • For example, these bivalve shells, probably arks Arcidae, each had a hole thru its umbo.

    Indian shell tools from Florida AYDIN 2009

  • The above magnified picture was taken from below the varix; the umbo was towards the top.

    Lessons learned from a specimen of Spisula solidissima AYDIN 2007

  • The above magnified picture was taken from below the varix; the umbo was towards the top.

    Archive 2007-10-01 AYDIN 2007

  • The Romans called the point at which the cord connecting the fetus with the placenta was cut and tied off the umbilicus, from umbo, “knob, projection.”

    No Uncertain Terms William Safire 2003

  • The Romans called the point at which the cord connecting the fetus with the placenta was cut and tied off the umbilicus, from umbo, “knob, projection.”

    No Uncertain Terms William Safire 2003

  • The Romans called the point at which the cord connecting the fetus with the placenta was cut and tied off the umbilicus, from umbo, “knob, projection.”

    No Uncertain Terms William Safire 2003

  • Their coverings having now been removed, on each shield a carving of the head of Caesar could be seen on the umbo, or central knob.

    Herodias 2003

  • The Romans called the point at which the cord connecting the fetus with the placenta was cut and tied off the umbilicus, from umbo, “knob, projection.”

    No Uncertain Terms William Safire 2003

Comments

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  • 1. a boss on a shield, as one at the center of a circular shield, or any similar boss or protuberance.

    2. in zoology, the beak of a bivalve shell; the protuberance of each valve above the hinge.

    3. in anatomy, the depressed area on the outer surface of the tympanic membrane.

    4. a blunt or rounded protuberance arising from a surface, as on a pine cone scale.

    Etymologically related, not surprisingly, to umbilicus.

    March 27, 2007

  • A mogul's what skiers call a hump -

    A term for a glorified bump.

    The kids like them jumbo

    But I'll take an umbo -

    Content with a notional jump.

    December 16, 2014