Definition of hadal in English:

hadal

Pronunciation /ˈhādl/ /ˈheɪdl/

adjective

  • Relating to the zone of the sea greater than approximately 20,000 feet (6,000 m) in depth (chiefly oceanic trenches).

    ‘The hadal environment (water depths greater than 6000m) is one of the last habitats on earth to be impacted by unsustainable human activity.’
    • ‘Submarine trenches usually develop downward from depths around 6,000 m, the beginning of the hadal region, exclusive domain of highly specialized and exquisite molluscan communities.’
    • ‘The hadal zone makes up only 1 or 2 percent of the ocean and is located in narrow oceanic trenches.’

Origin

1950s from Hades+ -al.