Designating a region of the open water of seas and oceans which is at great depth but away from the sea floor; (of an organism) living in such a…

Of or pertaining to ocean-depths exceeding 1000 fathoms.

of, pertaining to, or found in this region.

pertaining to the zone between the continental shelf and the abyssal zone (see quots.).

of, relating to, or inhabiting the psychrosphere.