1. Having irreversible brain damage with accompanying loss of brain function.
2. Informal Having little intelligence or interest; stupid or indifferent: "Office, pub, telly, bed, week after week. Ten years of that, and they're brain-dead" (Jane Stevenson).
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.