• WordNet 3.6
    • n umbo a slight rounded elevation where the malleus attaches to the eardrum
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Webster's Revised Unabridged Dictionary
    • Umbo 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.
    • Umbo (Zoöl) One of the lateral prominences just above the hinge of a bivalve shell.
    • Umbo The boss of a shield, at or near the middle, and usually projecting, sometimes in a sharp spike.
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Century Dictionary and Cyclopedia
    • n umbo The boss of a shield, central in the case of a circular shield. The umbo was sometimes hollow, convex toward the outer side and within allowing the hand to pass into the hollow and grasp a transverse bar; this form occurs especially in small round shields (see buckler); sometimes the umbo terminated in a spike which was a formidable weapon of offense.
    • n umbo A boss or knob. In botany, the knob in the center of the pileus or cap of an agaricoid fungus.
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Chambers's Twentieth Century Dictionary
    • n Umbo um′bō the boss of a shield: a knob: the point of a bivalve shell immediately above the hinge
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Webster's Revised Unabridged Dictionary
Chambers's Twentieth Century Dictionary


In literature:

It seems to me almost useless to send the fragments of the shell to the British Museum to be named, more especially as the umbo has been lost.
"More Letters of Charles Darwin Volume II" by Charles Darwin
The central umbo or crest posteriorly is a marked feature.
"Narrative Of The Voyage Of H.M.S. Rattlesnake, Commanded By The Late Captain Owen Stanley, R.N., F.R.S. Etc. During The Years 1846-1850. Including Discoveries And Surveys In New Guinea, The Louisiade Archipelago, Etc. To Which Is Added The Account Of Mr. E.B. Kennedy's Expedition For The Exploration Of The Cape York Peninsula. By John Macgillivray, F.R.G.S. Naturalist To The Expedition. In Two Volumes. Volume 1." by John MacGillivray
They are sometimes bell-shaped and then flattened, often with a mound or umbo.
"Among the Mushrooms" by Ellen M. Dallas and Caroline A. Burgin
The =pileus= becomes convex, and expanded or nearly flat, and often with an elevation or umbo in the center.
"Studies of American Fungi. Mushrooms, Edible, Poisonous, etc." by George Francis Atkinson
The position of the umbo on the apophysis is the basis of Koehne's subdivision of the section Haploxylon.
"The Genus Pinus" by George Russell Shaw
Many plants have a marked umbo on the top of the cap and the rim of the cap may be slightly turned up.
"The Mushroom, Edible and Otherwise" by M. E. Hard
A ridge, generally runs from the umbo to the upper point.
"A Monograph on the Sub-class Cirripedia (Volume 1 of 2)" by Charles Darwin
P. 4-6 cm., umbo very strong, ochraceous, scaly; g. white; s. 9-15 cm.
"European Fungus Flora: Agaricaceae" by George Massee
The umbo is the oldest part of the valve.
"Elementary Zoology, Second Edition" by Vernon L. Kellogg

In news:

Characterization of ossicular chain vibration at the umbo: Implications for a middle ear microelectromechanical system design.
Characterization of ossicular chain vibration at the umbo: Implications for a middle ear microelectromechanical system design.
Characterization of ossicular chain vibration at the umbo : Implications for a middle ear microelectromechanical system design.