malleus

noun

1. The small hammer-shaped bone of the middle ear.

   “A fracture of the malleus handle is a rare traumatic middle ear lesion.”

   “The tympanic cavity is spanned by the three smallest bones in the body: the auditory ossicles[…] These bones, named for their shape, are the malleus (malʹe-us; "hammer"); the incus (ingʹkus; "anvil"); and the stapes (staʹpēz; "stirrup"). The "handle" of the malleus is secured to the eardrum, and the base of the stapes fits into the oval window.”

2. The tripus (ossicle in cypriniform fishes).
3. One of the paired calcareous structures within the mastax of rotifers.

   “[…] in the typical mastax of a Brachionus there are two hammer-like bodies (mallei), which work on a kind of split anvil (incus); […] each malleus consists of an upper part or head (uncus) and a lower or handle (manubrium);”