01 n. The boss of a shield, at or near the middle, and usually projecting, sometimes in a sharp spike.
pl.
Umbones, Umbos ((#))
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1.
The boss of a shield, at or near the middle, and usually projecting, sometimes in a sharp spike.
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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.
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3.
One of the lateral prominences just above the hinge of a bivalve shell.(Zool.)