Source : Webster's Revised Unabridged Dictionary (1913)

Thalamus \Thal"a*mus\, n.; pl. {Thalami}. [L. thalamus chamber,
   Gr. qa`lamos.]
   1. (Anat.) A mass of nervous matter on either side of the
      third ventricle of the brain; -- called also {optic
      thalamus}.

   2. (Bot.)
      (a) Same as {Thallus}.
      (b) The receptacle of a flower; a torus.

Source : WordNet®

thalamus
     n : large egg-shaped structures of gray matter that form the
         dorsal subdivision of the diencephalon
     [also: {thalami} (pl)]