1. of or relating to the deepest parts of the ocean, especially ocean trenches deeper than 6,000 meters
Usage: technical; oceanography

Examples

• Hadal zones are home to some of the most extreme life forms on Earth.
• The hadal depths of the Mariana Trench remain largely unexplored.
• Hadal organisms have adapted to crushing pressure and near-freezing temperatures.
• Scientists study hadal ecosystems to understand life in extreme environments.
• The hadal region represents less than 1% of the ocean floor.