Source : Webster's Revised Unabridged Dictionary (1913)

Ossiculum \Os*sic"u*lum\, n.; pl. {Ossicula}. [L., a little
   bone.] (Zo["o]l.)
   Same as {Ossicle}.

Source : WordNet®

ossiculum
     n : a small bone; especially one in the middle ear [syn: {ossicle},
          {bonelet}]