of or relating to the greatest ocean depths, below approximately 20,000 feet (6500 meters).
of or relating to the biogeographic region of the ocean bottom below the abyssal zone.
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Origin of hadal
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Word Origin for hadal
C20: from French, from Hadés Hades
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Relating to the deepest regions of the ocean, below about 6,000 m (19,680 ft). The hadal zone mostly comprises trenches that can reach depths greater than 10,000 m (32,800 ft).
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.