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n. pl. um·bo·nes (ŭm-bō′nēz) or um·bos
1. The boss or knob at the center of a shield.
a. 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.
b. Anatomy A small projection at the center of the outer surface of the eardrum.

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

um′bo·nal (ŭm′bə-nəl, ŭm-bō′nəl) adj.


n, pl umbones (ʌmˈbəʊniːz) or umbos
1. (Botany) a small hump projecting from the centre of the cap in certain mushrooms
2. (Zoology) a hooked prominence occurring at the apex of each half of the shell of a bivalve mollusc
3. (Anatomy) anatomy the slightly convex area at the centre of the outer surface of the eardrum, where the malleus is attached on the internal surface
4. (Arms & Armour (excluding Firearms)) a large projecting central boss on a shield, esp on a Saxon shield
[C18: from Latin: boss of a shield, projecting piece]
umbonate, umbonal, umbonic adj


(ˈʌm boʊ)

n., pl. um•bo•nes (ʌmˈboʊ niz) um•bos.
1. a boss on a shield.
2. any similar boss or protuberance.
3. the beak of a bivalve shell; the protuberance of each valve above the hinge.
4. the raised area on the inner surface of the tympanic membrane, where the malleus is attached.
[1715–25; < Latin umbō; akin to umbilīcus (see umbilicus)]
um′bo•nal (-bə nl) adj.
um′bo•nate (-nɪt, -ˌneɪt) adj.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.umbo - a slight rounded elevation where the malleus attaches to the eardrumumbo - a slight rounded elevation where the malleus attaches to the eardrum
eardrum, myringa, tympanic membrane, tympanum - the membrane in the ear that vibrates to sound
convex shape, convexity - a shape that curves or bulges outward
References in classic literature ?
On a day, so far back that there was no way of estimating its distance, one, Somo, son of Loti, who was the chief of the island fortress of Umbo, had quarrelled with his father and fled from his wrath along with a dozen canoe-loads of young men.
The umbo is shifted anteriorly and is located at a distance of a quarter of the length of the entire hinge line.
Contract notice: Building cleaning services (maintenance cleaning for the properties umbo i & Ii and kandinsky house in berlin, Federal agency for real estate tasks, (voek 110-17)
Three methods are commonly used for aging bivalve molluscs: counting external growth rings on the shell surface from the umbo to the ventral margin (Stevenson & Dickie 1954, MacDonald & Thompson 1988), counting growth increments from the peak to the base of the pyramid-shaped calcareous portion of the shell hinge ligament (Trueman 1953, Merrill et al.
Biometric analysis: The shell length (SL = line straight distance from umbo to ventral margin of the shell, mm) and weight (g) of each clam were measured in situ with a caliper (0.
5 cm diam, hemispherical to plano-convex, with obtuse umbo, dark brown in the centre fading towards camel brown at margin, fibrillose, margin entire; surface smooth, shiny, viscid.
In the laboratory, morphological features of each specimen including shell morphology, umbo, lunule, radial ribs, posterior slope, escutcheon, hinge ligament, growth lines and cardinal teeth were recorded.
Este analisis lo hemos cotejado con la cronologia aportada por la presencia de ciertos materiales, entre los que destaca un plato de barniz rojo de borde vuelto sin pie y con un leve umbo (tipo 1-A2) que, en la zona de Murcia, tienen un horizonte encuadrable entre comienzos del IV a.
The umbo is a tiny depression in the very centre of the foveola.
En postlarvas de 225 [micro]m de longitud y 315 [micro]m de altura, la muesca del biso fue muy evidente en el extremo izquierdo de la concha, con el desarrollo de las auriculas en los extremos laterales del umbo (Fig.
Modern art's new muse was the shop window dummy, celebrated in photographs by Umbo (Fig.
Mussel shells were first sectioned through the umbo and epoxied to a microscope slide or plexiglass plate, depending on size.