brain death

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Irreversible brain damage and loss of brain function, as evidenced by cessation of breathing and other vital reflexes, unresponsiveness to stimuli, absence of muscle activity, and a flat electroencephalogram for a specific length of time.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun medicine An irreversible loss of brain function and cessation of brain activity.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun death when respiration and other reflexes are absent; consciousness is gone; organs can be removed for transplantation before the heartbeat stops