a·bys·sal (ə-bĭsəl)
adj.
► Abysmal; unfathomable.
► Of or relating to the great depths of the oceans.
► Of or relating to the region of the ocean bottom between the bathyal and hadal zones, from depths of approximately 3,000 to 6,000 meters (10,000 to 20,000 feet).

[TahlilGaran] American Dictionary ▲