1. A room or enclosure with acoustically reflective walls used in broadcasting and recording to produce echoes or similar sound effects.
2. An institution or environment in which one set of views predominates and dissenting viewpoints are squelched, ridiculed, or ignored: “Napoleon's vision of himself as a ‘superior man' had been confirmed to him time and again by events and by the echo chamber of his own propaganda machine” (David A. Bell).
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. 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.