Umbo

WORDNET DICTIONARY

umbo(n = noun.body) - a slight rounded elevation where the malleus attaches to the eardrum;

is a kind of convex shape, convexity

Umbo, n. [L.].

The boss of a shield, at or near the middle, and usually projecting, sometimes in a sharp spike. [1913 Webster]
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. [1913 Webster]
One of the lateral prominences just above the hinge of a bivalve shell. [1913 Webster]

Umbo, n. (pl. -os or umbones)
1 the boss of a shield, esp. in the centre.
2 Bot. & Zool. a rounded knob or protuberance.

Derivative

umbonal adj. umbonate adj.

Etymology

L umbo -onis

For further exploring for "Umbo" in Webster Dictionary Online