ˈəm(ˌ)bō noun
( plural umbo·nes ˌəmˈbō(ˌ)nēz ; or umbos )
Etymology: Latin — more at navel
1. : the boss of a shield sometimes having a sharp spike
2. : a rounded elevation often accompanied by a corresponding depression on the opposite surface: as
a. : an elevation in the tympanic membrane of the ear
b. : an elevation in a cone scale of a pine tree
3. : one of the lateral prominences just above the hinge of a bivalve shell : beak 1d(1)