Of or relating to the deepest regions of the ocean, below about 6,000 meters (20,000 feet).
Designating or of the ecological zone (hadal zone) of the ocean floor trenches below c. 19,685 ft (c. 6,000 m)
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).
Origin of hadal
French from Hadès Hades from Greek Haidēs weid- in Indo-European roots