Source : Webster's Revised Unabridged Dictionary (1913)

Manubrium \Ma*nu"bri*um\, n.; pl. L. {Manubria}, E.
   {Manubriums}. [L., handle, fr. manus hand.]
   1. (Anat.) A handlelike process or part; esp., the anterior
      segment of the sternum, or presternum, and the handlelike
      process of the malleus.

   2. (Zo["o]l.) The proboscis of a jellyfish; -- called also
      {hypostoma}. See Illust. of {Hydromedusa}.

Source : WordNet®

manubrium
     n : the upper part of the breastbone
     [also: {manubria} (pl)]