n.
- The most anterior of the three primary regions of the embryonic brain from which the telencephalon and diencephalon develop.
- The segment of the adult brain that develops from the embryonic forebrain and includes the cerebrum, thalamus, and hypothalamus.
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.