From The Collaborative International Dictionary of English v.0.48 [gcide]:
Malleus \Mal"le*us\, n.; pl. Mallei. [L., hammer. See Mall a
beetle.]
1. (Anat.) The outermost of the three small auditory bones,
ossicles; the hammer. It is attached to the tympanic
membrane by a long process, the handle or manubrium. See
Illust. of Far.
[1913 Webster]
2. (Zool.) One of the hard lateral pieces of the mastax of
Rotifera. See Mastax.
[1913 Webster]
3. (Zool.) A genus of bivalve shells; the hammer shell.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
malleus
n 1: the ossicle attached to the eardrum [syn: malleus,
hammer]