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Of or relating to the deepest regions of the ocean, below about 6,000 meters (20,000 feet).

[French, from Hadès, Hades, from Greek Haidēs; see weid- in Indo-European roots.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Physical Geography) of, relating to, or constituting the zones of the oceans deeper than abyssal: below about 6000 metres (18 000 ft). See also abyssal
[C20: from French, from Hadés Hades]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈheɪd l)

of or pertaining to the biogeographic region of the ocean bottom below the abyssal zone, or from approximately 20,000 ft. (6500 m) to the greatest ocean depths.
[1955–60; Had (es) + -al1]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Adj.1.hadal - relating to the deepest parts of the ocean (below 6000 meters)
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
References in periodicals archive ?
In the new study, researchers wanted to use bomb carbon as a tracer for organic material in hadal trenches to better understand the organisms that live there.
"This was a big moment for hadal science and really demonstrated the scientific capability of the submersible.
"We hope to work with our collaborators at NASA's Jet Propulsion Laboratory to develop autonomy and algorithms to enable the Orpheus class of hadal vehicles to explore intelligently and cooperatively alongside other vehicles and the researchers that operate them," Machado said.
In their pioneering work on the hadal waters, Mantyla and Reid (2) succeeded in hadal water sampling at ~10000 m depth by applying specially designed free-vehicle instruments for the measurement of hydrographic properties (temperature, salinity, dissolved oxygen, and nutrients) in the Marianas Trench area (11-13[degrees]N, 142-146[degrees]E) of the western Pacific Ocean.
Zone Depth Environment Nematode (m) abundance Arabian Sea 400 Upwelling 1.700 Southeast 75-100 Upwelling -- continental 100-150 shelf of India Continental 305 OMZ 1.502 [+ or -] 430 shelf Peru (12[degrees]S) Atacama Trench 1.050 Bathyal 498 [+ or -] 157 depths 7.800 Hadal 5.072 [+ or -] 2.344 depths Continental 88 OMZ 1.193-2.417 shelf central 120 OMZ 738-1.268 Chile Continental 126 OMZ 1.555-3.077 shelf central Chile Continental 80 Seasonal 2.136 [+ or -] 633 shelf, hypoxia Valparaiso Bay 100 Seasonal 1.528 [+ or -] 138 hypoxia 140 Seasonal 1.687 [+ or -] 69 hypoxia Zone Total Reference meiofauna Arabian Sea -- Cook et al.
In 2009 Katherine Abu Hadal had her first taste of Yemeni food at a nondescript restaurant in Sana'a.
Flatfish are primarily a littoral order with some bathyal representatives, but they lack an abyssal species, let alone a hadal one (1).
Alleged Al-Qaeda operative Khaled Hadal Al-Qahtani, who figured high on a list of 47 most-wanted terrorists, surrendered in May this year to Saudi security authorities.
The prints represent both scientific data, rarely seen images of geothermal activity in the abyssal and hadal zones, and formal compositions, elegant black-and-white abstractions.
The trip to the floor of the Marianas Trench took them from the sunlit world to the ebony-black abyss of the "hadal zone," beginning at approximately 20,000 feet.
It lies in the hadal zone beyond the abyssal zone, and plunges down to a water depth of around 11 kilometers.