The Collaborative International Dictionary of English v.0.48:
Interbrain \In`ter*brain`\, n. (Anat.) See Thalamencephalon. [1913 Webster]WordNet (r) 3.0 (2006):
interbrain n 1: the posterior division of the forebrain; connects the cerebral hemispheres with the mesencephalon [syn: diencephalon, interbrain, betweenbrain, thalmencephalon]