incus
noun
in·cus ˈiŋ-kəs 
plural incudes iŋ-ˈkyü-(ˌ)dēz ˈiŋ-kyə-ˌdēz
ˈiŋ-kyə-ˌdēz : the middle bone of a chain of three small bones in the ear of a mammal
called also anvil
see ear illustration
Example Sentences
Recent Examples on the Web The smallest bones are inside your ear, and they are known as the hammer (malleus), stirrup (stapes), and anvil (incus). 
Jason Bittel, Washington Post, 20 Oct. 2019 The auditory ossicles of the middle ear – the malleus, incus and stapes – are the tiniest bones in the human body. Emily Matchar, Smithsonian, 18 Dec. 2017
Jason Bittel, Washington Post, 20 Oct. 2019 The auditory ossicles of the middle ear – the malleus, incus and stapes – are the tiniest bones in the human body. Emily Matchar, Smithsonian, 18 Dec. 2017 Word History
Etymology
borrowed from New Latin incūd-, incūs, going back to Latin, "anvil," from in- in- entry 2 + -cūd-, -cūs, root noun from the stem of cūdere "to beat, strike, hammer" — more at hew
Note: The Latin name incūs "anvil" was first applied to the bone from its resemblance to an anvil by Andreas vesalius, in De humanis corporis fabrica libri septem (Basil, 1543), pp. 34-35; for details see C.D. O'Malley and Edwin Clarke, "The discovery of auditory ossicles," Bulletin of the History of Medicine, vol. 35, no. 5 (September-October, 1961), pp. 419-41. Regarding the semantic structure of the compound incūs, see note at anvil.
First Known Use
1615, in the meaning defined above
Medical Definition
incus
noun
in·cus ˈiŋ-kəs
plural incudes iŋ-ˈkyüd-(ˌ)ēz ˈiŋ-kyə-ˌdēz
ˈiŋ-kyə-ˌdēz : the middle bone of the chain of three ossicles in the middle ear of a mammal resembling a premolar tooth with the body having a facet which articulates with the malleus and with the longer of the two widely separated crura having a process which articulates with the stapes
called also ambos, anvil