1. Relating to the region of deep water which excludes the ocean floor, floating in the ocean depths and living in the oceanic water column at depths of between 4,000 and 6,000 meters (13,120 feet to 19,680 feet), and seaward of the shelf-slope break: The marine biologists used specialized mechanical diving equipment to explore the abyssopelagic depths of the sea.
2. Of or relating to organisms or phenomena in midwater, but still at great depths: At the abyssopelagic deepness of the sea, many of the creatures are blind.